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Exhibit 10.11

2,500,000 Shares

NORTH AMERICAN SCIENTIFIC, INC.

Common Stock

UNDERWRITING AGREEMENT

        December 13, 2000

CIBC WORLD MARKETS CORP.
UBS WARBURG LLC
LEERINK SWANN & COMPANY     on behalf of the Several
Underwriters named on
Schedule I attached hereto
c/o CIBC World Markets Corp.
One World Financial Center
New York, New York 10281

Ladies and Gentlemen:

        North American Scientific, Inc., a Delaware corporation (the "Company")
and the Selling Stockholders listed on Schedule II attached hereto (the "Selling
Stockholders"), propose, subject to the terms and conditions contained herein,
to sell to you and the other underwriters named on Schedule I attached hereto
(the "Underwriters"), for whom you are acting as Representatives (the
"Representatives"), an aggregate of 2,500,000 shares (the "Firm Shares") of the
Company's Common Stock, $0.01 par value (the "Common Stock"). Of the 2,500,000
Firm Shares, 2,320,000 shares are to be issued and sold by the Company and
180,000 shares are to be sold by the Selling Stockholders. The respective
amounts of the Firm Shares to be purchased by each of the several Underwriters
are set forth opposite their names on Schedule I attached hereto. In addition,
the Company proposes to grant to the Underwriters an option to purchase up to an
additional 375,000 shares (the "Option Shares") of Common Stock from the Company
for the purpose of covering over-allotments in connection with the sale of the
Firm Shares. The Firm Shares and the Option Shares are together called the
"Shares."

1.    Sale and Purchase of the Shares.

        On the basis of the representations, warranties and agreements contained
in, and subject to the terms and conditions of, this Agreement:

        (a)  The Company agrees to sell to each of the Underwriters, and each of
the Underwriters agrees, severally and not jointly, to purchase from the
Company, at a price of $17.875 per share (the "Initial Price"), the number of
Firm Shares set forth opposite the name of such Underwriter under the column
"Number of Firm Shares to be Purchased from the Company" on Schedule I to this
Agreement, subject to adjustment in accordance with Section 11 hereof. Each of
the Selling Stockholders agrees, severally and not jointly, to sell to the
Underwriters, at the Initial Price, the number of Firm Shares set forth opposite
the name of such Selling Stockholder under the Column "Number of Firm Shares to
be Sold By Each Selling Stockholder" on Schedule II attached hereto, and each of
the Underwriters agrees, severally and not jointly, to purchase from the Selling
Stockholders, at the Initial Price, the number of Firm Shares set forth opposite
the name of such Underwriter under the column "Number of Firm Shares to be
Purchased from the Selling Stockholders" on Schedule II attached hereto, subject
to adjustment in accordance with Section 11 hereof.

        (b)  The Company grants to the several Underwriters an option to
purchase, severally and not jointly, all or any part of the Option Shares at the
Initial Price. The number of Option Shares to

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be purchased by each Underwriter shall be the same percentage (adjusted by the
Representatives to eliminate fractions) of the total number of Option Shares to
be purchased by the Underwriters as such Underwriter is purchasing of the Firm
Shares. Such option may be exercised only to cover over-allotments in the sales
of the Firm Shares by the Underwriters and may be exercised in whole or in part
at any time on or before 12:00 noon, New York City time, on the business day
before the Firm Shares Closing Date (as defined below), and from time to time
thereafter within 30 days after the date of this Agreement, in each case upon
written, facsimile or telegraphic notice, or verbal or telephonic notice
confirmed by written, facsimile or telegraphic notice, by the Representatives to
the Company no later than 12:00 noon, New York City time, on the business day
before the Firm Shares Closing Date or at least two business days before the
Option Shares Closing Date (as defined below), as the case may be, setting forth
the number of Option Shares to be purchased and the time and date (if other than
the Firm Shares Closing Date) of such purchase.

2.    Delivery and Payment. Delivery by the Company and the Selling Stockholders
of the Firm Shares to the Representatives for the respective accounts of the
Underwriters, and payment of the purchase price by wire transfer payable in New
York Clearing House (same day) funds drawn to the order of the Company for the
shares purchased from the Company and to the Selling Stockholders for the shares
purchased from the Selling Stockholders, against delivery of the respective
certificates therefor to the Representatives, shall take place at the offices of
CIBC World Markets Corp., One World Financial Center, New York, New York 10281,
at 10:00 a.m., New York City time, on the third business day following the date
of this Agreement, or at such time on such other date, not later than 10
business days after the date of this Agreement, as shall be agreed upon by the
Company and the Representatives (such time and date of delivery and payment are
called the "Firm Shares Closing Date").

        In the event the option with respect to the Option Shares is exercised
in whole or in part on one or more occasions, delivery by the Company of the
Option Shares to the Representatives for the respective accounts of the
Underwriters and payment of the purchase price thereof in immediately available
funds by wire transfer payable in New York Clearing House (same day) funds to
the Company shall take place at the offices of CIBC World Markets Corp.
specified above at the time and on the date (which may be the same date as, but
in no event shall be earlier than, the Firm Shares Closing Date) specified in
the notice referred to in Section 1(b) (such time and date of delivery and
payment are called the "Option Shares Closing Date"). The Firm Shares Closing
Date and the Option Shares Closing Date are called, individually, a "Closing
Date" and, together, the "Closing Dates."

        Certificates evidencing the Shares shall be registered in such names and
shall be in such denominations as the Representatives shall request at least two
full business days before the Firm Shares Closing Date or, in the case of Option
Shares, on the day of notice of exercise of the option as described in
Section l(b) and shall be made available to the Representatives for checking and
packaging, at such place as is designated by the Representatives, on the full
business day before the Firm Shares Closing Date (or the Option Shares Closing
Date in the case of the Option Shares).

3.    Registration Statement and Prospectus; Public Offering. The Company has
prepared and filed in conformity with the requirements of the Securities Act of
1933, as amended (the "Securities Act"), and the published rules and regulations
thereunder (the "Rules") adopted by the Securities and Exchange Commission (the
"Commission") a Registration Statement (as hereinafter defined) on Form S-3
(No. 333-48192), including a preliminary prospectus relating to the Shares, and
such amendments thereof as may have been required to the date of this Agreement.
Copies of such Registration Statement (including all amendments thereof) and of
the related Preliminary Prospectus (as hereinafter defined) have heretofore been
delivered by the Company to you. The term "Preliminary Prospectus" means any
preliminary prospectus (as described in Rule 430 of the Rules) included at any
time as a part of the Registration Statement or filed with the Commission by the
Company with the consent of

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the Representatives pursuant to Rule 424(a) of the Rules. The term "Registration
Statement" as used in this Agreement means the initial registration statement
(including all exhibits, financial schedules and information deemed to be a part
of the Registration Statement through incorporation by reference or otherwise),
as amended at the time and on the date it becomes effective (the "Effective
Date") including the information (if any) deemed to be part thereof at the time
of effectiveness pursuant to Rule 430A of the Rules. If the Company has filed an
abbreviated registration statement to register additional Shares pursuant to
Rule 462(b) under the Rules (the "462(b) Registration Statement") then any
reference herein to the Registration Statement shall also be deemed to include
such 462(b) Registration Statement. The term "Prospectus" as used in this
Agreement means the prospectus in the form included in the Registration
Statement at the time of effectiveness or, if Rule 430A of the Rules is relied
on, the term Prospectus shall also include the final prospectus filed with the
Commission pursuant to Rule 424(b) of the Rules.

        The Company and the Selling Stockholders understand that the
Underwriters propose to make a public offering of the Shares, as set forth in
and pursuant to the Prospectus, as soon after the Effective Date and the date of
this Agreement as the Representatives deem advisable. The Company and the
Selling Stockholders hereby confirm that the Underwriters and dealers have been
authorized to distribute or cause to be distributed each Preliminary Prospectus
and are authorized to distribute the Prospectus (as from time to time amended or
supplemented if the Company furnishes amendments or supplements thereto to the
Underwriters).

4.    Representations and Warranties of the Company. The Company hereby
represents and warrants to each Underwriter as follows:

        (a)  On the Effective Date, the Registration Statement complied, and on
the date of the Prospectus, the date any post-effective amendment to the
Registration Statement becomes effective, the date any supplement or amendment
to the Prospectus is filed with the Commission and each Closing Date, the
Registration Statement and the Prospectus (and any amendment thereof or
supplement thereto) will comply, in all material respects, with the applicable
provisions of the Securities Act and the Rules and the Securities Exchange Act
of 1934, as amended (the "Exchange Act"), and the rules and regulations of the
Commission thereunder. The Registration Statement did not, as of the Effective
Date, contain any untrue statement of a material fact or omit to state any
material fact required to be stated therein or necessary in order to make the
statements therein not misleading; and on the Effective Date and the other dates
referred to above neither the Registration Statement nor the Prospectus, nor any
amendment thereof or supplement thereto, will contain any untrue statement of a
material fact or will omit to state any material fact required to be stated
therein or necessary in order to make the statements therein not misleading.
When any related preliminary prospectus was first filed with the Commission
(whether filed as part of the Registration Statement or any amendment thereto or
pursuant to Rule 424(a) of the Rules) and when any amendment thereof or
supplement thereto was first filed with the Commission, such preliminary
prospectus as amended or supplemented complied in all material respects with the
applicable provisions of the Securities Act and the Rules and did not contain
any untrue statement of a material fact or omit to state any material fact
required to be stated therein or necessary in order to make the statements
therein not misleading. Notwithstanding the foregoing, none of the
representations and warranties in this paragraph 4(a) shall apply to statements
in, or omissions from, the Registration Statement or the Prospectus made in
reliance upon, and in conformity with, information herein or otherwise furnished
in writing by the Representatives on behalf of the several Underwriters for use
in the Registration Statement or the Prospectus. With respect to the preceding
sentence, the Company acknowledges that the only information furnished in
writing by the Representatives on behalf of the several Underwriters for use in
the Registration Statement or the Prospectus is the paragraph with respect to
stabilization on the inside front cover page of the Prospectus and the
statements contained under the caption "Underwriting" in the Prospectus.

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        (b)  The Registration Statement is effective under the Securities Act
and no stop order preventing or suspending the effectiveness of the Registration
Statement or suspending or preventing the use of the Prospectus has been issued
and no proceedings for that purpose have been instituted or are threatened under
the Securities Act. Any required filing of the Prospectus and any supplement
thereto pursuant to Rule 424(b) of the Rules has been or will be made in the
manner and within the time period required by such Rule 424(b).

        (c)  The documents incorporated by reference in the Registration
Statement and the Prospectus, at the time they were filed with the Commission,
complied in all material respects with the requirements of the Exchange Act and,
when read together and with the other information in the Registration Statement
and the Prospectus, do not contain an untrue statement of a material fact or
omit to state a material fact required to be stated therein or necessary in
order to make the statements therein, in the light of the circumstances under
which they were made, not misleading.

        (d)  The financial statements of the Company (including all notes and
schedules thereto) included or incorporated by reference in the Registration
Statement and Prospectus present fairly the financial position, the results of
operations, the statements of cash flows and the statements of stockholders'
equity and the other information purported to be shown therein of the Company
and its Subsidiaries (as hereinafter defined) at the respective dates and for
the respective periods to which they apply; and such financial statements and
related schedules and notes have been prepared in conformity with generally
accepted accounting principles, consistently applied throughout the periods
involved, and all adjustments necessary for a fair presentation of the results
for such periods have been made. The summary and selected financial data
included in the Prospectus present fairly the information shown therein as at
the respective dates and for the respective periods specified and the summary
and selected financial data have been presented on a basis consistent with the
consolidated financial statements so set forth in the Prospectus and other
financial information.

        (e)  To the best of the Company's knowledge, PricewaterhouseCoopers,
LLP, whose reports are filed with the Commission as a part of the Registration
Statement, are and, during the periods covered by their reports, were
independent public accountants as required by the Securities Act and the Rules.

        (f)    The Company and each of its Subsidiaries is a corporation duly
organized, validly existing and in good standing under the laws of the state of
the jurisdiction of its incorporation. The Company and each such subsidiary or
other entity controlled directly or indirectly by the Company (collectively,
"Subsidiaries") is duly qualified to do business and is in good standing as a
foreign corporation in each jurisdiction in which the nature of the business
conducted by it or location of the assets or properties owned, leased or
licensed by it requires such qualification, except for such jurisdictions where
the failure to so qualify would not have a material adverse effect on the assets
or properties, business, results of operations or financial condition of the
Company (a "Material Adverse Effect"). The Company does not own, lease or
license any asset or property or conduct any business outside the United States
of America. The Company and each of its Subsidiaries has all requisite corporate
power and authority, and all necessary authorizations, approvals, consents,
orders, licenses, certificates and permits of and from all governmental or
regulatory bodies or any other person or entity (collectively, the "Permits"),
to own, lease and license its assets and properties and conduct its business,
all of which are valid and in full force and effect, as described in the
Registration Statement and the Prospectus, except where the lack of such
Permits, individually or in the aggregate, would not have a Material Adverse
Effect. The Company and each of its Subsidiaries has fulfilled and performed in
all material respects all of its material obligations with respect to such
Permits and no event has occurred that allows, or after notice or lapse of time
would allow, revocation or termination thereof or results in any other material
impairment of the rights of the Company thereunder. Except as may be required
under the

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Securities Act and state and foreign Blue Sky laws, no other Permits are
required to enter into, deliver and perform this Agreement and to issue and sell
the Shares.

        (g)  The Company and each of its Subsidiaries own or possess adequate
and enforceable rights to use all patents, patent applications, trademarks,
trademark applications, trade names, service marks, copyrights, copyright
applications, licenses, know-how and other similar rights and proprietary
knowledge (collectively, "Intangibles") described in the Prospectus as being
owned by them necessary for the conduct of their businesses. Neither the Company
nor any of its Subsidiaries has received any notice of, or is not aware of, any
infringement of or conflict with asserted rights of others with respect to any
Intangibles.

        (h)  The Company and each of its Subsidiaries have good and marketable
title in fee simple to all items of real property and good and marketable title
to all personal property described in the Prospectuses as being owned by them.
Any real property and buildings described in the Prospectuses as being held
under lease by the Company and each of its Subsidiaries is held by them under
valid, existing and enforceable leases, free and clear of all liens,
encumbrances, claims, security interests and defects, except such as are
described in the Registration Statement and the Prospectus or would not have a
Material Adverse Effect.

        (i)    There are no litigation or governmental proceedings to which the
Company or its Subsidiaries is subject or which is pending or, to the knowledge
of the Company, threatened, against the Company or any of its Subsidiaries,
which, individually or in the aggregate, might have a Material Adverse Effect,
affect the consummation of this Agreement or which is required to be disclosed
in the Registration Statement and the Prospectus that is not so disclosed.

        (j)    Subsequent to the respective dates as of which information is
given in the Registration Statement and the Prospectus, except as described
therein, (a) there has not been any material adverse change with regard to the
assets or properties, business, results of operations or financial condition of
the Company; (b) neither the Company nor any of its Subsidiaries has sustained
any loss or interference with its assets, businesses or properties (whether
owned or leased) from fire, explosion, earthquake, flood or other calamity,
whether or not covered by insurance, or from any labor dispute or any court or
legislative or other governmental action, order or decree which would have a
Material Adverse Effect; and (c) since the date of the latest balance sheet
included in the Registration Statement and the Prospectus, except as reflected
therein, neither the Company nor any of its Subsidiaries has (i) issued any
securities or incurred any liability or obligation, direct or contingent, for
borrowed money, except such liabilities or obligations incurred in the ordinary
course of business, (ii) entered into any transaction not in the ordinary course
of business or (iii) declared or paid any dividend or made any distribution on
any shares of its stock or redeemed, purchased or otherwise acquired or agreed
to redeem, purchase or otherwise acquire any shares of its stock.

        (k)  There is no document, contract or other agreement of a character
required to be described in the Registration Statement or Prospectus or to be
filed as an exhibit to the Registration Statement which is not described or
filed as required by the Securities Act or Rules. Each description of a
contract, document or other agreement in the Registration Statement and the
Prospectus accurately reflects in all material respects the terms of the
underlying document, contract or agreement. Each agreement described in the
Registration Statement and Prospectus or listed in the Exhibits to the
Registration Statement or incorporated by reference is in full force and effect
and is valid and enforceable by and against the Company or a Subsidiary, as the
case may be, in accordance with its terms, except as the enforceability thereof
may be limited by applicable bankruptcy, insolvency, reorganization, moratorium
or other similar laws affecting the enforcement of creditors' rights generally
and by general equitable principles. Neither the Company nor any Subsidiary, if
such Subsidiary is a party, nor to the Company's knowledge, any other party is
in

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default in the observance or performance of any term or obligation to be
performed by it under any such agreement, and no event has occurred which with
notice or lapse of time or both would constitute such a default, in any such
case which default or event, individually or in the aggregate, would have a
Material Adverse Effect. No default exists, and no event has occurred which with
notice or lapse of time or both would constitute a default, in the due
performance and observance of any term, covenant or condition, by the Company or
any Subsidiary, if such Subsidiary is a party thereto, of any other agreement or
instrument to which the Company or any Subsidiary is a party or by which it or
its the Company, any Subsidiary or their respective properties or business may
be bound or affected which default or event, individually or in the aggregate,
would have a Material Adverse Effect.

        (l)    Neither the Company nor any of its Subsidiaries is in violation
of any term or provision of its charter or by-laws or of any franchise, license,
permit, judgment, decree, order, statute, rule or regulation, where the
consequences of such violation, individually or in the aggregate, would have a
Material Adverse Effect.

        (m)  Neither the execution, delivery and performance of this Agreement
by the Company nor the consummation of any of the transactions contemplated
hereby (including, without limitation, the issuance and sale by the Company of
the Shares) will give rise to a right to terminate or accelerate the due date of
any payment due under, or conflict with or result in the breach of any term or
provision of, or constitute a default (or an event which with notice or lapse of
time or both would constitute a default) under, or require any consent or waiver
under, or result in the execution or imposition of any lien, charge or
encumbrance upon any properties or assets of the Company or any of its
Subsidiaries pursuant to the terms of, any indenture, mortgage, deed of trust or
other agreement or instrument to which the Company or any of its Subsidiaries is
a party or by which either the Company or any of its Subsidiaries or any of
their properties or businesses is bound, or any franchise, license, permit,
judgment, decree, order, statute, rule or regulation applicable to the Company
or any of its Subsidiaries or violate any provision of the charter or by-laws of
the Company or any of its Subsidiaries, except for such consents or waivers
which have already been obtained and are in full force and effect.

        (n)  The Company has authorized and outstanding capital stock as set
forth under the caption "Capitalization" in the Prospectus. The certificates
evidencing the Shares are in due and proper legal form and have been duly
authorized for issuance by the Company. All of the issued and outstanding shares
of Common Stock have been duly and validly issued and are fully paid and
nonassessable. There are no statutory preemptive or other similar rights to
subscribe for or to purchase or acquire any shares of Common Stock of the
Company or any of its Subsidiaries or any such rights pursuant to their
respective Certificates of Incorporation or by-laws or any agreement or
instrument to or by which the Company or any of its Subsidiaries is a party or
bound. The Shares, when issued and sold pursuant to this Agreement, will be duly
and validly issued, fully paid and nonassessable and none of them will be issued
in violation of any preemptive or other similar right. Except as disclosed in
the Registration Statement and the Prospectus, there is no outstanding option,
warrant or other right calling for the issuance of, and there is no commitment,
plan or arrangement to issue, any share of stock of the Company or its
Subsidiaries or any security convertible into, or exercisable or exchangeable
for, such stock. The Common Stock and the Shares conform in all material
respects to all statements in relation thereto contained in the Registration
Statement and the Prospectus. All outstanding shares of capital stock of each
Subsidiary have been duly authorized and validly issued, and are fully paid and
nonassessable and are owned directly by the Company or by another wholly-owned
subsidiary of the Company free and clear of any security interests, liens,
encumbrances, equities or claims, other than those described in the Prospectus.

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        (o)  Other than the Selling Stockholders, no holder of any security of
the Company has the right to have any security owned by such holder included in
the Registration Statement or to demand registration of any security owned by
such holder during the period ending 90 days after the date of this Agreement.
Each five percent stockholder, director and executive officer of the Company
have delivered to the Representatives such person's enforceable written lock-up
agreement.

        (p)  All necessary corporate action has been duly and validly taken by
the Company to authorize the execution, delivery and performance of this
Agreement and the issuance and sale of the Shares by the Company. This Agreement
has been duly and validly authorized, executed and delivered by the Company and
constitutes and will constitute the legal, valid and binding obligation of the
Company enforceable against the Company in accordance with its terms, except as
the enforceability thereof may be limited by bankruptcy, insolvency,
reorganization, moratorium or other similar laws affecting the enforcement of
creditors' rights generally and by general equitable principles.

        (q)  Neither the Company nor any of its Subsidiaries is involved in any
labor dispute nor, to the knowledge of the Company, is any such dispute
threatened, which dispute would have a Material Adverse Effect. The Company is
not aware of any existing or imminent labor disturbance by the employees of any
of its principal suppliers or contractors which would have a Material Adverse
Effect. The Company is not aware of any threatened or pending litigation between
the Company or any of its Subsidiaries and any of its executive officers which,
if adversely determined, could have a Material Adverse Effect and has no reason
to believe that such officers will not remain in the employment of the Company.

        (r)  No transaction has occurred between or among the Company and any of
its officers, directors or five percent stockholders or any affiliate or
affiliates of any such officer, director or five percent stockholders that is
required to be described in and is not described in the Registration Statement
and the Prospectus.

        (s)  The Company has not taken, nor will it take, directly or
indirectly, any action designed to or which might reasonably be expected to
cause or result in, or which has constituted or which might reasonably be
expected to constitute, the stabilization or manipulation of the price of the
Common Stock to facilitate the sale or resale of any of the Shares.

        (t)    The Company and its Subsidiaries have filed all Federal, state,
local and foreign tax returns which are required to be filed through the date
hereof, or has received extensions thereof, and has paid all taxes shown on such
returns and all assessments received by it to the extent that the same are
material and have become due. There are no tax audits or investigations pending,
which if adversely determined would have a Material Adverse Effect; nor are
there any material proposed additional tax assessments against the Company or
any of its Subsidiaries.

        (u)  The Shares have been duly authorized for quotation on the National
Association of Securities Dealers Automated Quotation ("Nasdaq") National Market
System, subject to official Notice of Issuance.

        (v)  Intentionally omitted.

        (w)  The books, records and accounts of the Company and each of its
Subsidiaries accurately and fairly reflect, in reasonable detail, the
transactions in, and dispositions of, the assets of, and the results of
operations of, the Company and each of its Subsidiaries. The Company and each of
its Subsidiaries maintains a system of internal accounting controls sufficient
to provide reasonable assurances that (i) transactions are executed in
accordance with management's general or specific authorizations,
(ii) transactions are recorded as necessary to permit preparation of financial
statements in accordance with generally accepted accounting principles and to
maintain asset

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accountability, (iii) access to assets is permitted only in accordance with
management's general or specific authorization and (iv) the recorded
accountability for assets is compared with the existing assets at reasonable
intervals and appropriate action is taken with respect to any differences.

        (x)  The Company and each of its Subsidiaries are insured by insurers of
recognized financial responsibility against such losses and risks and in such
amounts as are customary in the businesses in which they are engaged or propose
to engage after giving effect to the transactions described in the Prospectus;
all policies of insurance and fidelity or surety bonds insuring the Company or
any of its Subsidiaries or the Company's or its Subsidiaries' respective
businesses, assets, employees, officers and directors are in full force and
effect; the Company and each of its Subsidiaries are in compliance with the
terms of such policies and instruments in all material respects; and neither the
Company nor any Subsidiary of the Company has reason to believe that it will be
able to renew its existing insurance coverage as and when such coverage expires
or obtain similar coverage from similar insurers as may be necessary to continue
its business at a cost that would not have a Material Adverse Effect. Neither
the Company nor any Subsidiary has been denied any insurance coverage which it
has sought or for which it has applied.

        (y)  Each approval, consent, order, authorization, designation,
declaration or filing of, by or with any regulatory, administrative or other
governmental body necessary in connection with the execution and delivery by the
Company of this Agreement and the consummation of the transactions herein
contemplated required to be obtained or performed by the Company (except such
additional steps as may be required by the National Association of Securities
Dealers, Inc. (the "NASD") or may be necessary to qualify the Shares for public
offering by the Underwriters under the state securities or Blue Sky laws) has
been obtained or made and is in full force and effect.

        (z)  There are no affiliations with the NASD among the Company's
officers, directors or, to the knowledge of the Company, any five percent or
greater stockholder of the Company, except as set forth in the Registration
Statement or otherwise disclosed in writing to the Representatives.

        (aa)(i) Each of the Company and its Subsidiaries are in compliance in
all material respects with all rules, laws and regulation relating to the
development, testing, manufacturing, sale and distribution of products regulated
by the U.S. Food and Drug Administration, or similar state or foreign government
agency, the use, treatment, storage and disposal of toxic substances and
protection of health or the environment ("Environmental Law") which are
applicable to its business; (ii) neither the Company nor its Subsidiaries has
received any notice from any governmental authority or third party of an
asserted claim under Environmental Laws; (iii) each of the Company and its
Subsidiaries have received all permits, licenses or other approvals required of
it under applicable Environmental Laws to conduct its business and is in
compliance with all terms and conditions of any such permit, license or
approval; (iv) to the Company's knowledge, no facts currently exist that will
require the Company or its Subsidiaries to make future material capital
expenditures to comply with Environmental Laws; and (v) no property which is or
has been owned, leased or occupied by the Company or its Subsidiaries has been
designated as a Superfund site pursuant to the Comprehensive Environmental
Response, Compensation of Liability Act of 1980, as amended (42 U.S.C.
Section 9601, et. seq.) or otherwise designated as a contaminated site under
applicable state or local law. Neither the Company nor any of its Subsidiaries
has been named as a "potentially responsible party" under the CERCLA 1980.

        (bb)In the ordinary course of its business, the Company periodically
reviews the effect of Environmental Laws on the business, operations and
properties of the Company and its Subsidiaries, to identify and evaluate
associated costs and liabilities (including, without limitation, any capital or
operating expenditures required for clean-up, closure of properties or
compliance with Environmental Laws, or any permit, license or approval, any
related constraints on operating

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activities and any potential liabilities to third parties). On the basis of such
review, the Company has no reason to believe that such associated costs and
liabilities would not, singly or in the aggregate, have a Material Adverse
Effect.

        (cc)The Company is not and, after giving effect to the offering and sale
of the Shares and the application of proceeds thereof as described in the
Prospectus, will not be an "investment company" within the meaning of the
Investment Company Act of 1940, as amended (the "Investment Company Act").

        (dd)The Company, its Subsidiaries or any other person associated with or
acting on behalf of the Company or its Subsidiaries including, without
limitation, any director, officer, agent or employee of the Company or any of
its Subsidiaries has not, directly or indirectly, while acting on behalf of the
Company or any of its Subsidiaries (i) used any corporate funds for unlawful
contributions, gifts, entertainment or other unlawful expenses relating to
political activity; (ii) made any unlawful payment to foreign or domestic
government officials or employees or to foreign or domestic political parties or
campaigns from corporate funds; (iii) violated any provision of the Foreign
Corrupt Practices Act of 1977, as amended; or (iv) made any other unlawful
payment.

        (ee)The Company and each of its Subsidiaries maintain a system of
internal accounting controls sufficient to provide reasonable assurance that
(1) transactions are executed in accordance with management's general or
specific authorization; (2) transactions are recorded as necessary to permit
preparation of financial statements in conformity with generally accepted
accounting principles and to maintain asset accountability; (3) access to assets
is permitted only in accordance with management's general or specific
authorization; and (4) recorded accountability for assets is compared with the
existing assets at reasonable intervals and appropriate action is taken with
respect to any differences.

5.    Representations and Warranties of the Selling Stockholders. Each of the
Selling Stockholders hereby represents and warrants to each Underwriter as
follows:

        (a)  Such Selling Stockholder has caused certificates for the number of
Shares to be sold by such Selling Stockholder hereunder to be delivered to North
American Scientific, Inc. as custodian (the "Custodian"), endorsed in blank or
with blank stock powers duly executed, with a signature appropriately
guaranteed, such certificates to be held in custody by the Custodian for
delivery, pursuant to the provisions of this Agreement and agreements dated
December    , 2000, among the Custodian and each of the Selling Stockholders
(the "Custody Agreements").

        (b)  Each Selling Stockholder has granted an irrevocable power of
attorney (the "Power of Attorney") to the person named therein, on behalf of
such Selling Stockholder, to execute and deliver this Agreement and any other
document necessary or desirable in connection with the transactions contemplated
hereby and to deliver the shares to be sold by such Selling Stockholder pursuant
hereto.

        (c)  This Agreement, the Custody Agreements, the Powers of Attorney and
the Lock-Up Agreements have each been duly authorized, executed and delivered by
or on behalf of each Selling Stockholder and, assuming due authorization,
execution and delivery by the other parties hereto, constitutes the valid and
legally binding agreement of such Selling Stockholder, enforceable against such
Selling Stockholder in accordance with its terms.

        (d)  The execution and delivery by each Selling Stockholder of this
Agreement and the performance by such Selling Stockholder of its obligations
under this Agreement (i) will not contravene any provision of applicable law,
statute, regulation or filing or any agreement or other instrument binding upon
such Selling Stockholder or any judgment, order or decree of any governmental
body, agency or court having jurisdiction over such Selling Stockholder,
(ii) does not require any consent, approval, authorization or order of or
registration or filing with any court or

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governmental agency or body having jurisdiction over it, except such as may be
required by the Blue Sky laws of the various states in connection with the offer
and sale of the Shares which have been or will be effected in accordance with
this Agreement, (iii) does not and will not violate any statute, law, regulation
or filing or judgment, injunction, order or decree applicable to such Selling
Stockholder or (iv) will not result in the creation or imposition of any lien,
charge or encumbrance upon any property or assets of such Selling Stockholder
pursuant to the terms of any agreement or instrument to which such Selling
Stockholder is a party or by which such Selling Stockholder may be bound or to
which any of the property or assets of such Selling Stockholder is subject.

        (e)  Each Selling Stockholder has, and on the Firm Shares Closing Date
will have, valid and marketable title to the Shares to be sold by such Selling
Stockholder free and clear of any lien, claim, security interest or other
encumbrance, including, without limitation, any restriction on transfer, except
as otherwise described in the Registration Statement and Prospectus.

        (f)    Each Selling Stockholder has, and on the Firm Shares Closing Date
will have, full legal right, power and authorization, and any approval required
by law, to sell, assign, transfer and deliver the Shares to be sold by such
Selling Stockholder in the manner provided by this Agreement.

        (g)  Upon delivery of and payment for the Shares to be sold by each
Selling Stockholder pursuant to this Agreement, the several Underwriters will
receive valid and marketable title to such Shares free and clear of any lien,
claim, security interest or other encumbrance.

        (h)  All information relating to each Selling Stockholder furnished in
writing by such Selling Stockholder expressly for use in the Registration
Statement and Prospectus is, and on each Closing Date will be, true, correct,
and complete, and does not, and on each Closing Date will not, contain any
untrue statement of a material fact or omit to state any material fact necessary
to make such information not misleading.

        (i)    Each Selling Stockholder has reviewed the Registration Statement
and Prospectus and, although such Selling Stockholder has not independently
verified the accuracy or completeness of all the information contained therein,
nothing has come to the attention of such Selling Stockholder that would lead
such Selling Stockholder to believe that (i) on the Effective Date, the
Registration Statement contained any untrue statement of a material fact or
omitted to state any material fact required to be stated therein in order to
make the statements made therein not misleading and (ii) on the Effective Date
the Prospectus contained and, on each Closing Date contains, no untrue statement
of a material fact or omitted or omits to state any material fact necessary in
order to make the statements therein, in the light of the circumstances under
which they were made, misleading.

        (j)    The sale of Shares by each Selling Stockholder pursuant to this
Agreement is not prompted by such Selling Stockholder's knowledge of any
material information concerning the Company or any of its Subsidiaries which is
not set forth in the Prospectus.

        (k)  Each Selling Stockholder has not taken and will not take, directly
or indirectly, any action designed to or that might reasonably be expected to
cause or result in stabilization or manipulation of the price of any security of
the Company to facilitate the sale or resale of the Shares.

        (l)    Each Selling Stockholder has no actual knowledge that any
representation or warranty of the Company set forth in Section 4 above is untrue
or inaccurate in any material respect.

        (m)  The representations and warranties of each Selling Stockholder in
the applicable Custody Agreement are, and on each Closing Date will be, true and
correct.

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6.    Conditions of the Underwriters' Obligations. The obligations of the
Underwriters under this Agreement are several and not joint. The respective
obligations of the Underwriters to purchase the Shares are subject to each of
the following terms and conditions:

        (a)  Notification that the Registration Statement has become effective
shall have been received by the Representatives and the Prospectus shall have
been timely filed with the Commission in accordance with Section 7(a) of this
Agreement.

        (b)  No order preventing or suspending the use of any preliminary
prospectus or the Prospectus shall have been or shall be in effect and no order
suspending the effectiveness of the Registration Statement shall be in effect
and no proceedings for such purpose shall be pending before or threatened by the
Commission, and any requests for additional information on the part of the
Commission (to be included in the Registration Statement or the Prospectus or
otherwise) shall have been complied with to the satisfaction of the Commission
and the Representatives.

        (c)  The representations and warranties of the Company and the Selling
Stockholders contained in this Agreement and in the certificates delivered
pursuant to Section 6(d) shall be true and correct when made and on and as of
each Closing Date as if made on such date. The Company and the Selling
Stockholders shall have performed all covenants and agreements and satisfied all
the conditions contained in this Agreement required to be performed or satisfied
by them at or before such Closing Date.

        (d)  The Representatives shall have received on each Closing Date a
certificate, addressed to the Representatives and dated such Closing Date, of
the chief executive or chief operating officer and the chief financial officer
or chief accounting officer of the Company to the effect that (i) the signers of
such certificate have carefully examined the Registration Statement, the
Prospectus and this Agreement and that the representations and warranties of the
Company in this Agreement are true and correct on and as of such Closing Date
with the same effect as if made on such Closing Date and the Company has
performed all covenants and agreements and satisfied all conditions contained in
this Agreement required to be performed or satisfied by it at or prior to such
Closing Date, and (ii) no stop order suspending the effectiveness of the
Registration Statement has been issued and to the best of their knowledge, no
proceedings for that purpose have been instituted or are pending under the
Securities Act.

        (e)  The Representatives shall have received on each Closing Date a
certificate, addressed to the Representatives and dated such Closing Date, of
each of the Selling Stockholders, to the effect that each such Selling
Stockholder has carefully examined the Registration Statement, the Prospectus
and this Agreement and that the representations and warranties of such Selling
Stockholder in this Agreement are true and correct on and as of such Closing
Date with the same effect as if made on such Closing Date and such Selling
Stockholder has performed all covenants and agreements and satisfied all
conditions contained in this Agreement required to be performed or satisfied by
it at or prior to such Closing Date.

        (f)    The Representatives shall have received, at the time this
Agreement is executed and on each Closing Date a signed letter from
PricewaterhouseCoopers LLP addressed to the Representatives and dated,
respectively, the date of this Agreement and each such Closing Date, in form and
substance reasonably satisfactory to the Representatives, confirming that they
are independent accountants within the meaning of the Securities Act and the
Rules, that the response to Item 10 of the Registration Statement is correct
insofar as it relates to them and stating in effect that:

        (i)    in their opinion the audited financial statements and financial
statement schedules included or incorporated by reference in the Registration
Statement and the Prospectus and

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reported on by them comply as to form in all material respects with the
applicable accounting requirements of the Securities Act and the Rules;

        (ii)  on the basis of a reading of the amounts included in the
Registration Statement and the Prospectus under the headings "Summary
Consolidated Financial Data" and "Selected Consolidated Financial Data,"
carrying out certain procedures (but not an examination in accordance with
generally accepted auditing standards) which would not necessarily reveal
matters of significance with respect to the comments set forth in such letter, a
reading of the minutes of the meetings of the stockholders and directors of the
Company, and inquiries of certain officials of the Company who have
responsibility for financial and accounting matters of the Company as to
transactions and events subsequent to the date of the latest audited financial
statements, except as disclosed in the Registration Statement and the
Prospectus, nothing came to their attention which caused them to believe that:

        (A)  the amounts in "Summary Consolidated Financial Data," and "Selected
Consolidated Financial Data" included in the Registration Statement and the
Prospectus do not agree with the corresponding amounts in the audited and
unaudited financial statements from which such amounts were derived; or

        (B)  with respect to the Company, there were, at a specified date not
more than three business days prior to the date of the letter, any increases in
the current liabilities and long-term liabilities of the Company or any
decreases in net income or in working capital or the stockholders' equity in the
Company, as compared with the amounts shown on the Company's audited balance
sheet for the fiscal year ended October 31, 1999 and the fiscal year ended
October 31, 1998 included in the Registration Statement;

        (iii)  they have performed certain other procedures as may be permitted
under Generally Acceptable Auditing Standards as a result of which they
determined that certain information of an accounting, financial or statistical
nature (which is limited to accounting, financial or statistical information
derived from the general accounting records of the Company) set forth in the
Registration Statement and the Prospectus and reasonably specified by the
Representatives agrees with the accounting records of the Company; and

        (iv)  based upon the procedures set forth in clauses (ii) and
(iii) above and a reading of the amounts included in the Registration Statement
under the headings "Summary Financial Data" and "Selected Financial Data"
included in the Registration Statement and Prospectus and a reading of the
financial statements from which certain of such data were derived, nothing has
come to their attention that gives them reason to believe that the "Summary
Financial Data" and "Selected Financial Data" included in the Registration
Statement and Prospectus do not comply as to the form in all material respects
with the applicable accounting requirements of the Securities Act and the Rules
or that the information set forth therein is not fairly stated in relation to
the financial statements included in the Registration Statement or Prospectus
from which certain of such data were derived are not in conformity with
generally accepted accounting principles applied on a basis substantially
consistent with that of the audited financial statements included in the
Registration Statement and Prospectus.

        References to the Registration Statement and the Prospectus in this
paragraph (f) are to such documents as amended and supplemented at the date of
the letter.

        (g)  The Representatives shall have received on each Closing Date from
D'Ancona & Pflaum, LLC, counsel for the Company, an opinion, addressed to the
Representatives and dated such Closing Date, and stating in effect that:

        (i)    Each of the Company and its Subsidiaries have been duly organized
and is validly existing as a corporation in good standing under the laws of the
state of the jurisdiction of its

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incorporation. Each of the Company and its Subsidiaries is duly qualified and in
good standing as a foreign corporation in each jurisdiction in which the
character or location of its assets or properties (owned, leased or licensed) or
the nature of its businesses makes such qualification necessary, except for such
jurisdictions where the failure to so qualify, individually or in the aggregate,
would not have a Material Adverse Effect.

        (ii)  Each of the Company and its Subsidiaries has all requisite
corporate power and authority to own, lease or license its assets and its
properties and conduct its business as now being conducted and as described in
the Registration Statement and the Prospectus and, with respect to the Company,
to enter into, deliver and perform this Agreement and to issue and sell the
Shares.

        (iii)  The Company has authorized and issued capital stock as set forth
in the Registration Statement and the Prospectus under the caption
"Capitalization"; the certificates evidencing the Shares are in due and proper
legal form and have been duly authorized for issuance by the Company; all of the
outstanding shares of Common Stock of the Company have been duly and validly
authorized and issued and are fully paid and nonassessable and none of them was
issued in violation of any preemptive or other similar right. The Shares when
issued and sold pursuant to this Agreement will be duly and validly issued,
outstanding, fully paid and nonassessable and none of them will have been issued
in violation of any preemptive or other similar right. To the best of such
counsel's knowledge, except as disclosed in the Registration Statement and the
Prospectus, there are no preemptive or other rights to subscribe for or to
purchase or any restriction upon the voting or transfer of any securities of the
Company pursuant to the Company's Certificate of Incorporation or by-laws or
other governing documents or any agreements or other instruments to which the
Company is a party or by which it is bound. To the best of such counsel's
knowledge, except as disclosed in the Registration Statement and the Prospectus,
there is no outstanding option, warrant or other right calling for the issuance
of, and no commitment, plan or arrangement to issue, any share of stock of the
Company or any security convertible into, exercisable for, or exchangeable for
stock of the Company. The Common Stock, the Shares and the Warrants conform in
all material respects to the descriptions thereof contained in the Registration
Statement and the Prospectus. The issued and outstanding shares of capital stock
of each of the Company's Subsidiaries have been duly authorized and validly
issued, are fully paid and nonassessable and, to the best of such counsel's
knowledge, are owned by the Company or by another wholly-owned subsidiary of the
Company, free and clear of any perfected security interest or any other security
interests, liens, encumbrances, equities or claims, other than those contained
in the Registration Statement and the Prospectus.

        (iv)  Each of the Lock-Up Agreements executed by the Company's
stockholders, directors and officers has been duly and validly delivered by such
persons and constitutes the legal, valid and binding obligation of each such
person enforceable against each such person in accordance with its terms, except
as the enforceability thereof may be limited by applicable bankruptcy,
insolvency, reorganization, moratorium or other similar laws affecting the
enforcement of creditors' rights generally and by general equitable principles.

        (v)  All necessary corporate action has been duly and validly taken by
the Company to authorize the execution, delivery and performance of this
Agreement and the issuance and sale of the Shares. This Agreement has been duly
and validly authorized, executed and delivered by the Company and this Agreement
constitutes the legal, valid and binding obligation of the Company enforceable
against the Company in accordance with its terms except as such enforceability
may be limited by applicable bankruptcy, insolvency, fraudulent conveyance,
reorganization, moratorium and other similar laws affecting the enforcement of
creditors' rights generally and by general equitable principles.

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        (vi)  Neither the execution, delivery and performance of this Agreement
by the Company nor the consummation of any of the transactions contemplated
hereby (including, without limitation, the issuance and sale by the Company of
the Shares) will give rise to a right to terminate or accelerate the due date of
any payment due under, or conflict with or result in the breach of any term or
provision of, or constitute a default (or any event which with notice or lapse
of time, or both, would constitute a default) under, or require consent or
waiver under, or result in the execution or imposition of any lien, charge,
claim, security interest or encumbrance upon any properties or assets of the
Company or the Subsidiary pursuant to the terms of any indenture, mortgage, deed
trust, note or other agreement or instrument of which such counsel is aware and
to which the Company or the Subsidiary is a party or by which either the Company
or the Subsidiary or any of their respective properties or businesses is bound,
or any franchise, license, permit, judgment, decree, order, statute, rule or
regulation of which such counsel is aware or violate any provision of the
charter or by-laws of the Company or the Subsidiary.

        (vii)To the best of such counsel's knowledge, no default exists, and no
event has occurred which with notice or lapse of time, or both, would constitute
a default, in the due performance and observance of any term, covenant or
condition by the Company of any indenture, mortgage, deed of trust, note or any
other agreement or instrument to which the Company is a party or by which it or
any of its assets or properties or businesses may be bound or affected, where
the consequences of such default, individually or in the aggregate, would have a
Material Adverse Effect.

        (viii)To the best of such counsel's knowledge, the Company and its
Subsidiaries are not in violation of any term or provision of their respective
charters or by-laws or any franchise, license, permit, judgment, decree, order,
statute, rule or regulation, where the consequences of such violation,
individually or in the aggregate, would have a Material Adverse Effect.

        (ix)  No consent, approval, authorization or order of any court or
governmental agency or regulatory body is required for the execution, delivery
or performance of this Agreement by the Company or the consummation of the
transactions contemplated hereby or thereby, except such as have been obtained
under the Securities Act and such as may be required under state securities or
Blue Sky laws in connection with the purchase and distribution of the Shares by
the Underwriters.

        (x)  To the best of such counsel's knowledge, there is no litigation or
governmental or other proceeding or investigation, before any court or before or
by any public body or board pending or threatened against, or involving the
assets, properties or businesses of, the Company which would have a Material
Adverse Effect.

        (xi)  The statements in the Prospectus under the captions "Description
of Capital Stock," "Business" and "Related Party Transactions," insofar as such
statements constitute a summary of documents referred to therein or matters of
law, are fair summaries in all material respects and accurately present the
information called for with respect to such documents and matters. Accurate
copies of all contracts and other documents required to be filed as exhibits to,
or described in, the Registration Statement have been so filed with the
Commission or are fairly described in the Registration Statement, as the case
may be.

        (xii)The Registration Statement, all preliminary prospectuses and the
Prospectus and each amendment or supplement thereto (except for the financial
statements and schedules and other financial and statistical data included
therein, as to which such counsel expresses no opinion) comply as to form in all
material respects with the requirements of the Securities Act and the Rules.

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        (xiii)The Registration Statement is effective under the Securities Act,
and no stop order suspending the effectiveness of the Registration Statement has
been issued and no proceedings for that purpose have been instituted or are
threatened, pending or contemplated. Any required filing of the Prospectus and
any supplement thereto pursuant to Rule 424(b) under the Securities Act has been
made in the manner and within the time period required by such Rule 424(b).

        (xiv)The Shares have been approved for listing on the Nasdaq National
Market.

        (xv)The capital stock of the Company conforms in all material respects
to the description thereof contained in the Prospectus under the caption
"Description of Capital Stock."

        (xvi)The Company is not an "investment company" or an entity controlled
by an "investment company" as such terms are defined in the Investment Company
Act of 1940, as amended.

        To the extent deemed advisable by such counsel, such counsel may rely as
to matters of fact on certificates of responsible officers of the Company and
public officials and on the opinions of other counsel satisfactory to the
Representatives as to matters which are governed by laws other than the laws of
the State of Illinois, the General Corporation Law of the State of Delaware and
the Federal laws of the United States; provided that such counsel shall state
that in their opinion the Underwriters and they are justified in relying on such
other opinions. Copies of such certificates and other opinions shall be
furnished to the Representatives and counsel for the Underwriters.

        In addition, such counsel shall state that such counsel has participated
in conferences with officers and other representatives of the Company,
representatives of the Representatives and representatives of the independent
certified public accountants of the Company, at which conferences the contents
of the Registration Statement and the Prospectus and related matters were
discussed and, although such counsel is not passing upon and does not assume any
responsibility for the accuracy, completeness or fairness of the statements
contained in the Registration Statement and the Prospectus (except as specified
in the foregoing opinion), on the basis of the foregoing, no facts have come to
the attention of such counsel which lead such counsel to believe that the
Registration Statement at the time it became effective (except with respect to
the financial statements and notes and schedules thereto and other financial
data, as to which such counsel need express no belief) contained any untrue
statement of a material fact or omitted to state a material fact required to be
stated therein or necessary to make the statements therein not misleading, or
that the Prospectus as amended or supplemented (except with respect to the
financial statements, notes and schedules thereto and other financial data, as
to which such counsel need make no statement) on the date thereof contained any
untrue statement of a material fact or omitted to state a material fact
necessary in order to make the statements therein, in the light of the
circumstances under which they were made, not misleading.

        (h)  The Representatives shall have received on each Closing Date from
Pillsbury, Madison & Sutro, L.P., special patent counsel for the Company and its
Subsidiaries, an opinion, addressed to the Representatives and dated such
Closing Date, and stating in effect that:

        We have acted as patent counsel to the Company and its Subsidiaries with
respect to the patent matters reflected on Schedule A attached hereto (the
"Relevant Patent Matters").

        We have read the Registration Statement and the Prospectus, including in
particular the portions of the Registration Statement and the Prospectus under
the captions "Risk Factors" and "Business" (such portions being referred to
herein, collectively, as the "Technology Portions").

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OPINIONS:

1.    The statements in the Technology Portions are accurate and fairly present
the matters of law and legal conclusions stated therein.

2.    Nothing has come to our attention which has caused us to believe that the
Technology Portions contain any untrue statement of a material fact with respect
to the patent position of the Company or its Subsidiaries, or omit to state any
material fact relating to the patent position of the Company or its
Subsidiaries.

3.    Nothing has come to our attention which has caused us to believe that
(a) any patent application referred to in the Relevant Patent Matters was not
properly prepared and filed, in accordance with all applicable legal and
procedural requirements, or is not in good standing, (b) the issued patents (the
"Issued Patents") referred to in the Relevant Patent Matters was not properly
obtained, in accordance with all applicable legal and procedural requirements,
or is not in good standing, (c) that any invention described in any patent
application or the issued patent is not held by the Company or its Subsidiaries,
as applicable, or (d) any relevant prior art has not been disclosed promptly to
the appropriate governmental agency.

4.    To our knowledge, the Company and its Subsidiaries have not received any
notice asserting any ownership rights contrary to those of the Company or its
Subsidiaries in any of the Relevant Patent Matters.

5.    To our knowledge, the Company and its Subsidiaries have not received any
notice challenging the validity or enforceability of any Relevant Patent Matter.

6.    To our knowledge, the Company and its Subsidiaries have not received any
notice of infringement of, or conflict with, rights or claims of others with
respect to any patent, trademark, service mark, trade name, copyright or
know-how.

7.    To our knowledge, other than proceedings (except re-examination, reissue
or interference proceedings) of the various patent and trademark offices, there
are no legal or governmental proceedings pending relating to any patent, patent
application, trade secret, trademark, service mark or other proprietary
information or materials of the Company or its Subsidiaries and, to our
knowledge, no such proceedings are threatened or contemplated by governmental
authorities or others.

        In addition, such counsel shall state that such counsel has participated
in conferences with officers and other representatives of the Company and its
Subsidiaries, representatives of the Representatives and representatives of the
independent public accountants of the Company, at which conferences the contents
of the Registration Statement and the Prospectus as they related to the matters
set forth in the foregoing opinion were discussed. While such counsel has not
undertaken to independently verify and does not assume any responsibility for
the accuracy, completeness or fairness of the statements contained in the
Registration Statement and the Prospectus (except as specified in the foregoing
opinion), on the basis of the foregoing, no facts have come to the attention of
such counsel with respect to the matters set forth in the foregoing opinion
which lead such counsel to believe that the Registration Statement at the time
it became effective (except with respect to the financial statements and notes
and schedules thereto and other financial data, as to which such counsel need
express no belief) contained any untrue statement of a material fact or omitted
to state a material fact required to be stated therein or necessary to make the
statements therein not misleading, or that the Prospectus as amended or
supplemented (except with respect to the financial statements, notes and
schedules thereto and other financial data, as to which such counsel need make
no statement) on the date thereof and the date of such opinion contained any
untrue statement of a material fact or omitted to state a material fact
necessary in order to make the statements therein, in the light of the
circumstances under which they were made, not misleading.

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        (i)    The Representatives shall have received on each Closing Date from
Mintz, Levin, Cohn, Ferris, Glovsky & Popeo, P.C., special regulatory counsel
for the Company and its Subsidiaries, an opinion, addressed to the
Representatives and dated such Closing Date, and stating in effect that:

        (i)    The statements under the captions "Risk Factors" and "Business"
in the Registration Statement and the Prospectus are in all material respects
accurate summaries of applicable U.S. federal law and regulation under the
Federal Food, Drug and Cosmetic Act, as amended, as applied by the U.S Food and
Drug Administration, subject to the qualifications set forth therein.

        (ii)  No facts have come to our attention that have caused us to believe
that the information contained under the captions "Risk Factors" and "Business"
in the Registration Statement at the time the Registration Statement became
effective contained any untrue statement of a material fact, or omitted to state
any material fact required to be stated therein or necessary in order to make
the statements therein, in light of the circumstances under which they were
made, not misleading.

        (iii)  We have no knowledge of any action, suit or proceeding threatened
by the U.S. Food and Drug Administration against the Company or any of its
Subsidiaries seeking limitation, suspension or revocation of any license,
permit, approval or authorization required by the Company or any Subsidiary to
conduct its business as described in the Registration Statement and Prospectus.

        (j)    The Representatives shall have received on the Firm Shares
Closing Date from D'Ancona & Pflaum, LLC, counsel for the Selling Stockholders,
an opinion, addressed to the Representatives and dated such Closing Date, and
stating in effect that:

        (i)    This Agreement has been duly and validly executed and delivered
by or on behalf of each of the Selling Stockholders.

        (ii)  This Agreement, the Custody Agreement, the Power of Attorney and
the Lock-Up Agreement each constitute the legal, valid and binding obligation of
each of the Selling Stockholders enforceable against each such Selling
Stockholder in accordance with its terms except as such enforceability may be
limited by applicable bankruptcy, insolvency, reorganization, moratorium or
other similar laws affecting the enforcement of creditors' rights generally and
by general equitable principles; and each of the Selling Stockholders have full
legal right and authority to enter into this Agreement and to sell, transfer and
deliver in the manner provided in this Agreement, the respective Shares to be
sold by each such Selling Stockholder hereunder.

        (iii)  The transfer and sale by each of the Selling Stockholders of the
Shares to be sold by each such Selling Stockholder as contemplated by this
Agreement will not conflict with, result in a breach of, or constitute a default
under any agreement or instrument known to such counsel to which such Selling
Stockholder is a party or by which such Selling Stockholder or any of its
properties may be bound, or any franchise, license, permit, judgment, decree,
order, statute, rule or regulation.

        (iv)  All of the Selling Stockholders' rights in the Shares to be sold
by each Selling Stockholder pursuant to this Agreement, have been transferred to
the Underwriters who have severally purchased such Shares pursuant to this
Agreement, free and clear of adverse claims, assuming for purposes of this
opinion that the Underwriters purchased the same in good faith without notice of
any adverse claims.

        (v)  No consent, approval, authorization, license, certificate, permit
or order of any court, governmental or regulatory agency, authority or body or
financial institution is required in

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connection with the performance of this Agreement by the Selling Stockholders or
the consummation of the transactions contemplated hereby, including the delivery
and sale of the Shares to be delivered and sold by the Selling Stockholders,
except such as may be required under state securities or blue sky laws in
connection with the purchase and distribution of the Shares by the several
Underwriters.

        To the extent deemed advisable by such counsel, they may rely as to
matters of fact on certificates of the Selling Stockholders and on the opinions
of other counsel satisfactory to the Representatives as to matters which are
governed by laws other than the laws of the State of the State of Delaware or
the Federal laws of the United States; provided that such counsel shall state
that in their opinion the Underwriters and they are justified in relying on such
other opinions. Copies of such certificates and other opinions shall be
furnished to the Representatives and counsel for the Underwriters.

        In addition, such counsel shall state that such counsel has participated
in conferences with officers and other representatives of the Company,
representatives of the Representatives and representatives of the independent
public accountants of the Company, at which conferences the contents of the
Registration Statement and the Prospectus and related matters were discussed.
While such counsel has not undertaken to independently verify and does not
assume any responsibility for the accuracy, completeness or fairness of the
statements contained in the Registration Statement and the Prospectus (except as
specified in the foregoing opinion), on the basis of the foregoing, no facts
have come to the attention of such counsel which lead such counsel to believe
that the Registration Statement at the time it became effective (except with
respect to the financial statements, notes and schedules thereto and other
financial data, as to which such counsel need express no belief) contained any
untrue statement of a material fact or omitted to state a material fact required
to be stated therein or necessary to make the statements therein not misleading,
or that the Prospectus as amended or supplemented (except with respect to the
financial statements, notes and schedules thereto and other financial data, as
to which such counsel need make no statement) on the date thereof and the date
of such opinion contained any untrue statement of a material fact or omitted to
state a material fact necessary in order to make the statements therein, in the
light of the circumstances under which they were made, not misleading.

        (k)  All proceedings taken in connection with the sale of the Firm
Shares and the Option Shares as herein contemplated shall be reasonably
satisfactory in form and substance to the Representatives, and their counsel and
the Underwriters shall have received from McDermott, Will & Emery a favorable
opinion, addressed to the Representatives and dated such Closing Date, with
respect to the Shares, the Registration Statement and the Prospectus, and such
other related matters, as the Representatives may reasonably request, and the
Company shall have furnished to McDermott, Will & Emery such documents as they
may reasonably request for the purpose of enabling them to pass upon such
matters.

        (l)    The Representatives shall have received copies of the Lock-up
Agreements executed by each entity or person described in Section 4(n).

        (m)  The Company and the Selling Stockholders shall have furnished or
caused to be furnished to the Representatives such further certificates or
documents as the Representatives shall have reasonably requested.

7.    Covenants of the Company.

        (a)  The Company covenants and agrees as follows:

        (i)    The Company will use its best efforts to cause the Registration
Statement, if not effective at the time of execution of this Agreement, and any
amendments thereto, to become effective as promptly as possible. The Company
shall prepare the Prospectus in a form approved by the Representatives and file
such Prospectus pursuant to Rule 424(b) under the

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Securities Act not later than the Commission's close of business on the second
business day following the execution and delivery of this Agreement, or, if
applicable, such earlier time as may be required by Rule 430A(a)(3) under the
Securities Act.

        (ii)  The Company shall promptly advise the Representatives in writing
(i) when any amendment to the Registration Statement shall have become
effective, (ii) of any request by the Commission for any amendment of the
Registration Statement or the Prospectus or for any additional information,
(iii) of the prevention or suspension of the use of any preliminary prospectus
or the Prospectus or of the issuance by the Commission of any stop order
suspending the effectiveness of the Registration Statement or the institution or
threatening of any proceeding for that purpose and (iv) of the receipt by the
Company of any notification with respect to the suspension of the qualification
of the Shares for sale in any jurisdiction or the initiation or threatening of
any proceeding for such purpose. The Company shall not file any amendment of the
Registration Statement or supplement to the Prospectus unless the Company has
furnished the Representatives a copy for its review prior to filing and shall
not file any such proposed amendment or supplement to which the Representatives
reasonably object. The Company shall use its best efforts to prevent the
issuance of any such stop order and, if issued, to obtain as soon as possible
the withdrawal thereof.

        (iii)  If, at any time when a prospectus relating to the Shares is
required to be delivered under the Securities Act and the Rules, any event
occurs as a result of which the Prospectus as then amended or supplemented would
include any untrue statement of a material fact or omit to state any material
fact necessary to make the statements therein in the light of the circumstances
under which they were made not misleading, or if it shall be necessary to amend
or supplement the Prospectus to comply with the Securities Act or the Rules, the
Company promptly shall prepare and file with the Commission, subject to the
second sentence of paragraph (ii) of this Section 7(a), an amendment or
supplement which shall correct such statement or omission or an amendment which
shall effect such compliance.

        (iv)  The Company shall make generally available to its security holders
and to the Representatives as soon as practicable, but not later than 45 days
after the end of the 12-month period beginning at the end of the fiscal quarter
of the Company during which the Effective Date occurs (or 90 days if such
12-month period coincides with the Company's fiscal year), an earning statement
(which need not be audited) of the Company, covering such 12-month period, which
shall satisfy the provisions of Section 11(a) of the Securities Act or Rule 158
of the Rules.

        (v)  The Company shall furnish to the Representatives and counsel for
the Underwriters, without charge, signed copies of the Registration Statement
(including all exhibits thereto and amendments thereof) and to each other
Underwriter a copy of the Registration Statement (without exhibits thereto) and
all amendments thereof and, so long as delivery of a prospectus by an
Underwriter or dealer may be required by the Securities Act or the Rules, as
many copies of any preliminary prospectus and the Prospectus and any amendments
thereof and supplements thereto as the Representatives may reasonably request.

        (vi)  The Company shall cooperate with the Representatives and their
counsel in endeavoring to qualify the Shares for offer and sale in connection
with the offering under the laws of such jurisdictions as the Representatives
may designate and shall maintain such qualifications in effect so long as
required for the distribution of the Shares; provided, however, that the Company
shall not be required in connection therewith, as a condition thereof, to
qualify as a foreign corporation or to execute a general consent to service of
process in any jurisdiction or subject itself to taxation as doing business in
any jurisdiction.

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        (vii)Without the prior written consent of CIBC World Markets Corp., for
a period of 180 days after the date of this Agreement, the Company and each of
its individual directors and executive officers shall not issue, sell or
register with the Commission (other than on Form S-8 or on any successor form),
or otherwise dispose of, directly or indirectly, any equity securities of the
Company (or any securities convertible into, exercisable for or exchangeable for
equity securities of the Company), except for the issuance of the Shares
pursuant to the Registration Statement and the issuance of shares pursuant to
the Company's existing stock option plan or bonus plan as described in the
Registration Statement and the Prospectus. In the event that during this period,
(i) any shares are issued pursuant to the Company's existing stock option plan
or bonus plan that are exercisable during such 180 day period or (ii) any
registration is effected on Form S-8 or on any successor form relating to shares
that are exercisable during such 180 period, the Company shall obtain the
written agreement of such grantee or purchaser or holder of such registered
securities that, for a period of 180 days after the date of this Agreement, such
person will not, without the prior written consent of CIBC World Markets Corp.,
offer for sale, sell, distribute, grant any option for the sale of, or otherwise
dispose of, directly or indirectly, or exercise any registration rights with
respect to, any shares of Common Stock (or any securities convertible into,
exercisable for, or exchangeable for any shares of Common Stock) owned by such
person.

        (viii)On or before completion of the offering of the Shares, the Company
shall make all filings required under applicable securities laws and by the
Nasdaq National Market (including any required registration under the Exchange
Act).

        (ix)  The Company will apply the net proceeds from the offering of the
Shares in the manner set forth under "Use of Proceeds" in the Prospectus.

        (b)  The Company agrees to pay, or reimburse if paid by the
Representatives, whether or not the transactions contemplated hereby are
consummated or this Agreement is terminated, all costs and expenses incident to
the public offering of the Shares and the performance of the obligations of the
Company under this Agreement including those relating to: (i) the preparation,
printing, filing and distribution of the Registration Statement including all
exhibits thereto, each preliminary prospectus, the Prospectus, all amendments
and supplements to the Registration Statement and the Prospectus, and the
printing, filing and distribution of this Agreement; (ii) the preparation and
delivery of certificates for the Shares to the Underwriters; (iii) the
registration or qualification of the Shares for offer and sale under the
securities or Blue Sky laws of the various jurisdictions referred to in
Section 7(a)(vi), including the reasonable fees and disbursements of counsel for
the Underwriters in connection with such registration and qualification and the
preparation, printing, distribution and shipment of preliminary and
supplementary Blue Sky memoranda; (iv) the furnishing (including costs of
shipping and mailing) to the Representatives and to the Underwriters of copies
of each preliminary prospectus, the Prospectus and all amendments or supplements
to the Prospectus, and of the several documents required by this Section to be
so furnished, as may be reasonably requested for use in connection with the
offering and sale of the Shares by the Underwriters or by dealers to whom Shares
may be sold; (v) the filing fees of the NASD in connection with its review of
the terms of the public offering and reasonable fees and disbursements of
counsel for the Underwriters in connection with such review; (vi) inclusion of
the Shares for quotation on the Nasdaq National Market; and (vii) all transfer
taxes, if any, with respect to the sale and delivery of the Shares by the
Company to the Underwriters. Subject to the provisions of Section 10, the
Underwriters agree to pay, whether or not the transactions contemplated hereby
are consummated or this Agreement is terminated, all costs and expenses incident
to the performance of the obligations of the Underwriters under this Agreement
not payable by the Company pursuant to the preceding sentence, including,
without limitation, the fees and disbursements of counsel for the Underwriters.

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8.    Indemnification.

        (a)  The Company and the Selling Stockholders agree, jointly and
severally, to indemnify and hold harmless each Underwriter and each person, if
any, who controls any Underwriter within the meaning of Section 15 of the
Securities Act or Section 20 of the Exchange Act against any and all losses,
claims, damages and liabilities, joint or several (including any reasonable
investigation, legal and other expenses incurred in connection with, and any
amount paid in settlement of, any action, suit or proceeding or any claim
asserted), to which they, or any of them, may become subject under the
Securities Act, the Exchange Act or other Federal or state law or regulation, at
common law or otherwise, insofar as such losses, claims, damages or liabilities
arise out of or are based upon (i) any untrue statement or alleged untrue
statement of a material fact contained in any preliminary prospectus, the
Registration Statement or the Prospectus or any amendment thereof or supplement
thereto, or in any Blue Sky application or other information or other documents
executed by the Company filed in any state or other jurisdiction to qualify any
or all of the Shares under the securities laws thereof (any such application,
document or information being hereinafter referred to as a "Blue Sky
Application") or arise out of or are based upon any omission or alleged omission
to state therein a material fact required to be stated therein or necessary to
make the statements therein not misleading, (ii) in whole or in part upon any
breach of the representations and warranties set forth in Section 4 hereof, or
(iii) in whole or in part upon any failure of the Company to perform any of its
obligations hereunder or under law; provided, however, that such indemnity shall
not inure to the benefit of any Underwriter (or any person controlling such
Underwriter) on account of any losses, claims, damages or liabilities arising
from the sale of the Shares to any person by such Underwriter if such untrue
statement or omission or alleged untrue statement or omission was made in such
preliminary prospectus, the Registration Statement or the Prospectus, or such
amendment or supplement thereto, or in any Blue Sky Application in reliance upon
and in conformity with information furnished in writing to the Company by the
Representatives on behalf of any Underwriter specifically for use therein.
Notwithstanding the foregoing, the liability of the Selling Stockholders
pursuant to the provisions of Section 8(a) shall be limited to an amount equal
to the aggregate net proceeds received by each Selling Stockholder from the sale
of the Shares sold by each such Selling Stockholder hereunder. This indemnity
agreement will be in addition to any liability which the Company and Selling
Stockholders may otherwise have.

        (b)  Each Underwriter agrees, severally and not jointly, to indemnify
and hold harmless the Company, the Selling Stockholders and each person, if any,
who controls the Company within the meaning of Section 15 of the Securities Act
or Section 20 of the Exchange Act, each director of the Company, and each
officer of the Company who signs the Registration Statement, to the same extent
as the foregoing indemnity from the Company and the Selling Stockholders to each
Underwriter, but only insofar as such losses, claims, damages or liabilities
arise out of or are based upon any untrue statement or omission or alleged
untrue statement or omission which was made in any preliminary prospectus, the
Registration Statement or the Prospectus, or any amendment thereof or supplement
thereto, contained in the (i) concession and reallowance figures appearing under
the caption "Underwriting" and (ii) the stabilization information contained
under the caption "Underwriting" in the Prospectus; provided, however, that the
obligation of each Underwriter to indemnify the Company or the Selling
Stockholders (including any controlling person, director or officer thereof)
shall be limited to the net proceeds received by the Company from such
Underwriter.

        (c)  Any party that proposes to assert the right to be indemnified under
this Section will, promptly after receipt of notice of commencement of any
action, suit or proceeding against such party in respect of which a claim is to
be made against an indemnifying party or parties under this Section, notify each
such indemnifying party of the commencement of such action, suit or

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proceeding, enclosing a copy of all papers served. No indemnification provided
for in Section 8(a) or 8(b) shall be available to any party who shall fail to
give notice as provided in this Section 8(c) if the party to whom notice was not
given was unaware of the proceeding to which such notice would have related and
was prejudiced by the failure to give such notice but the omission so to notify
such indemnifying party of any such action, suit or proceeding shall not relieve
it from any liability that it may have to any indemnified party for contribution
or otherwise than under this Section. In case any such action, suit or
proceeding shall be brought against any indemnified party and it shall notify
the indemnifying party of the commencement thereof, the indemnifying party shall
be entitled to participate in, and, to the extent that it shall wish, jointly
with any other indemnifying party similarly notified, to assume the defense
thereof, with counsel reasonably satisfactory to such indemnified party, and
after notice from the indemnifying party to such indemnified party of its
election so to assume the defense thereof and the approval by the indemnified
party of such counsel, the indemnifying party shall not be liable to such
indemnified party for any legal or other expenses, except as provided below and
except for the reasonable costs of investigation subsequently incurred by such
indemnified party in connection with the defense thereof. The indemnified party
shall have the right to employ its counsel in any such action, but the fees and
expenses of such counsel shall be at the expense of such indemnified party
unless (i) the employment of counsel by such indemnified party has been
authorized in writing by the indemnifying parties, (ii) the indemnified party
shall have been advised by counsel that there may be one or more legal defenses
available to it which are different from or in addition to those available to
the indemnifying party (in which case the indemnifying parties shall not have
the right to direct the defense of such action on behalf of the indemnified
party) or (iii) the indemnifying parties shall not have employed counsel to
assume the defense of such action within a reasonable time after notice of the
commencement thereof, in each of which cases the fees and expenses of counsel
shall be at the expense of the indemnifying parties. An indemnifying party shall
not be liable for any settlement of any action, suit, proceeding or claim
effected without its written consent, which consent shall not be unreasonably
withheld or delayed.

9.    Contribution. In order to provide for just and equitable contribution in
circumstances in which the indemnification provided for in Section 8(a) or 8(b)
is due in accordance with its terms but for any reason is held to be unavailable
to or insufficient to hold harmless an indemnified party under Section 8(a) or
8(b), then each indemnifying party shall contribute to the aggregate losses,
claims, damages and liabilities (including any investigation, legal and other
expenses reasonably incurred in connection with, and any amount paid in
settlement of, any action, suit or proceeding or any claims asserted, but after
deducting any contribution received by any person entitled hereunder to
contribution from any person who may be liable for contribution including,
without limitation, persons who control the Company within the meaning of
Section 15 of the Securities Act or Section 20(a) of the Exchange Act, officers
of the Company who signed the Registration Statement and directors of the
Company) to which the indemnified party may be subject in such proportion as is
appropriate to reflect the relative benefits received by the Company, the
Selling Stockholders and the Underwriters from the offering of the Shares or, if
such allocation is not permitted by applicable law or indemnification is not
available as a result of the indemnifying party not having received notice as
provided in Section 8 hereof, in such proportion as is appropriate to reflect
not only the relative benefits referred to above but also the relative fault of
the Company, the Selling Stockholders and the Underwriters in connection with
the statements or omissions which resulted in such losses, claims, damages,
liabilities or expenses, as well as any other relevant equitable considerations.
The relative benefits received by the Company, the Selling Stockholders and the
Underwriters shall be deemed to be in the same proportion as (x) the total
proceeds from the offering (net of underwriting discounts but before deducting
expenses) received by the Company or the Selling Stockholders, as set forth in
the table on the cover page of the Prospectus, bear to (y) the underwriting
discounts received by the Underwriters, as set forth in the table on the cover
page of the Prospectus. The relative fault of the Company, the Selling
Stockholders or the

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Underwriters shall be determined by reference to, among other things, whether
the untrue or alleged untrue statement of a material fact related to information
supplied by the Company, the Selling Stockholders or the Underwriters and the
parties' relative intent, knowledge, access to information and opportunity to
correct or prevent such statement or omission. The Company, the Selling
Stockholders and the Underwriters agree that it would not be just and equitable
if contribution pursuant to this Section 9 were determined by pro rata
allocation (even if the Underwriters were treated as one entity for such
purpose) or by any other method of allocation which does not take account of the
equitable considerations referred to above. Notwithstanding the provisions of
this Section 9, (i) in no case shall any Underwriter (except as may be provided
in the Agreement Among Underwriters) be liable or responsible for any amount in
excess of the underwriting discount applicable to the Shares purchased by such
Underwriter hereunder; (ii) the Company shall be liable and responsible for any
amount in excess of such underwriting discount; and (iii) in no case shall any
Selling Stockholder be liable and responsible for any amount in excess of the
aggregate net proceeds of the sale of Shares received by such Selling
Stockholder; provided, however, that no person guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the Securities Act)
shall be entitled to contribution from any person who was not guilty of such
fraudulent misrepresentation. For purposes of this Section 9, each person, if
any, who controls an Underwriter within the meaning of Section 15 of the
Securities Act or Section 20(a) of the Exchange Act shall have the same rights
to contribution as such Underwriter, and each person, if any, who controls the
Company within the meaning of the Section 15 of the Securities Act or
Section 20(a) of the Exchange Act, each officer of the Company who shall have
signed the Registration Statement and each director of the Company shall have
the same rights to contribution as the Company, subject in each case to clauses
(i) and (ii) in the immediately preceding sentence of this Section 9. Any party
entitled to contribution will, promptly after receipt of notice of commencement
of any action, suit or proceeding against such party in respect of which a claim
for contribution may be made against another party or parties under this
Section, notify such party or parties from whom contribution may be sought, but
the omission so to notify such party or parties from whom contribution may be
sought shall not relieve the party or parties from whom contribution may be
sought from any other obligation it or they may have hereunder or otherwise than
under this Section. No party shall be liable for contribution with respect to
any action, suit, proceeding or claim settled without its written consent. The
Underwriter's obligations to contribute pursuant to this Section 9 are several
in proportion to their respective underwriting commitments and not joint.

10.    Termination. This Agreement may be terminated with respect to the Shares
to be purchased on a Closing Date by the Representatives by notifying the
Company and the Selling Stockholders at any time:

        (a)  in the absolute discretion of the Representatives at or before any
Closing Date: (i) if on or prior to such date, any domestic or international
event or act or occurrence has materially disrupted, or in the opinion of the
Representatives will in the future materially disrupt, the securities markets;
(ii) if there has occurred any new outbreak or material escalation of
hostilities or other calamity or crisis the effect of which on the financial
markets of the United States is such as to make it, in the judgment of the
Representatives, inadvisable to proceed with the offering; (iii) if there shall
be such a material adverse change in general financial, political or economic
conditions or the effect of international conditions on the financial markets in
the United States is such as to make it, in the judgment of the Representatives,
inadvisable or impracticable to market the Shares; (iv) if trading in the Shares
has been suspended by the Commission or trading generally on the New York Stock
Exchange, Inc., on the American Stock Exchange, Inc. or the Nasdaq National
Market has been suspended or limited, or minimum or maximum ranges for prices
for securities shall have been fixed, or maximum ranges for prices for
securities have been required, by said exchanges or by order of the Commission,
the National Association of Securities Dealers, Inc., or any other governmental
or regulatory authority; or (v) if a banking moratorium

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has been declared by any state or Federal authority; or (vi) if, in the judgment
of the Representatives, there has occurred a Material Adverse Effect, or

        (b)  at or before any Closing Date, that any of the conditions specified
in Section 6 shall not have been fulfilled when and as required by this
Agreement.

        If this Agreement is terminated pursuant to any of its provisions,
neither the Company nor the Selling Stockholders shall be under any liability to
any Underwriter, and no Underwriter shall be under any liability to the Company,
except that (y) if this Agreement is terminated by the Representatives or the
Underwriters because of any failure, refusal or inability on the part of the
Company or the Selling Stockholders to comply with the terms or to fulfill any
of the conditions of this Agreement, the Company will reimburse the Underwriters
for all out-of-pocket expenses (including the reasonable fees and disbursements
of their counsel) incurred by them in connection with the proposed purchase and
sale of the Shares or in contemplation of performing their obligations hereunder
and (z) no Underwriter who shall have failed or refused to purchase the Shares
agreed to be purchased by it under this Agreement, without some reason
sufficient hereunder to justify cancellation or termination of its obligations
under this Agreement, shall be relieved of liability to the Company, the Selling
Stockholders or to the other Underwriters for damages occasioned by its failure
or refusal.

11.    Substitution of Underwriters. If one or more of the Underwriters shall
fail (other than for a reason sufficient to justify the cancellation or
termination of this Agreement under Section 10) to purchase on any Closing Date
the Shares agreed to be purchased on such Closing Date by such Underwriter or
Underwriters, the Representatives may find one or more substitute underwriters
to purchase such Shares or make such other arrangements as the Representatives
may deem advisable or one or more of the remaining Underwriters may agree to
purchase such Shares in such proportions as may be approved by the
Representatives, in each case upon the terms set forth in this Agreement. If no
such arrangements have been made by the close of business on the business day
following such Closing Date,

        (a)  if the number of Shares to be purchased by the defaulting
Underwriters on such Closing Date shall not exceed 10% of the Shares that all
the Underwriters are obligated to purchase on such Closing Date, then each of
the nondefaulting Underwriters shall be obligated to purchase such Shares on the
terms herein set forth in proportion to their respective obligations hereunder;
provided, that in no event shall the maximum number of Shares that any
Underwriter has agreed to purchase pursuant to Section 1 be increased pursuant
to this Section 11 by more than one-ninth of such number of Shares without the
written consent of such Underwriter, or

        (b)  if the number of Shares to be purchased by the defaulting
Underwriters on such Closing Date shall exceed 10% of the Shares that all the
Underwriters are obligated to purchase on such Closing Date, then the Company
shall be entitled to one additional business day within which it may, but is not
obligated to, find one or more substitute underwriters reasonably satisfactory
to the Representatives to purchase such Shares upon the terms set forth in this
Agreement.

        In any such case, either the Representatives or the Company shall have
the right to postpone the applicable Closing Date for a period of not more than
five business days in order that necessary changes and arrangements (including
any necessary amendments or supplements to the Registration Statement or
Prospectus) may be effected by the Representatives and the Company. If the
number of Shares to be purchased on such Closing Date by such defaulting
Underwriter or Underwriters shall exceed 10% of the Shares that all the
Underwriters are obligated to purchase on such Closing Date, and none of the
nondefaulting Underwriters or the Company shall make arrangements pursuant to
this Section within the period stated for the purchase of the Shares that the
defaulting Underwriters agreed to purchase, this Agreement shall terminate with
respect to the Shares to be purchased on such Closing Date without liability on
the part of any nondefaulting Underwriter to the Company or the Selling
Stockholders and without liability on the part of the Company, except in both
cases as provided in

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Sections 7(b), 8, 9 and 10. The provisions of this Section shall not in any way
affect the liability of any defaulting Underwriter to the Company or the
nondefaulting Underwriters arising out of such default. A substitute underwriter
hereunder shall become an Underwriter for all purposes of this Agreement.

12.    Miscellaneous. The respective agreements, representations, warranties,
indemnities and other statements of the Company or its officers, of the Selling
Stockholders and of the Underwriters set forth in or made pursuant to this
Agreement shall remain in full force and effect, regardless of any investigation
made by or on behalf of any Underwriter or the Company or the Selling
Stockholders or any of the officers, directors or controlling persons referred
to in Sections 8 and 9 hereof, and shall survive delivery of and payment for the
Shares. The provisions of Sections 7(b), 8, 9 and 10 shall survive the
termination or cancellation of this Agreement.

        This Agreement has been and is made for the benefit of the Underwriters,
the Company and the Selling Stockholders and their respective successors and
assigns, and, to the extent expressed herein, for the benefit of persons
controlling any of the Underwriters, or the Company, and directors and officers
of the Company, and their respective successors and assigns, and no other person
shall acquire or have any right under or by virtue of this Agreement. The term
"successors and assigns" shall not include any purchaser of Shares from any
Underwriter merely because of such purchase.

        All notices and communications hereunder shall be in writing and mailed
or delivered or by telephone or telegraph if subsequently confirmed in writing,
(a) if to the Representatives, c/o CIBC World Markets Corp., One World Financial
Center, New York, New York 10281 Attention: Michael Fekete, with a copy to
McDermott, Will & Emery, 2049 Century Park East, Suite 3400, Los Angeles,
California 90067, Attention: Mark J. Mihanovic, Esq., (b) if to the Company, to
its agent for service as such agent's address appears on the cover page of the
Registration Statement with a copy to D'Ancona & Pflaum, 111 East Wacker Drive,
Suite 2800, Chicago, Illinois 60601, Attention: Allan J. Reich, Esq., and (c) if
to the Selling Stockholders to                        ,
Attention:                                                 , with a copy
to                        , Attention:                        , Esq.

        This Agreement shall be governed by and construed in accordance with the
laws of the State of New York without regard to principles of conflict of laws.

        This Agreement may be signed in any number of counterparts, each of
which shall be an original, with the same effect as if the signatures thereto
and hereto were upon the same instrument.

SIGNATURES ON NEXT PAGE

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        Please confirm that the foregoing correctly sets forth the agreement
among us.

    Very truly yours,
 
 
NORTH AMERICAN SCIENTIFIC, INC.
 
 
By:
 
 
 
         

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        Title:                

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SELLING STOCKHOLDER

 

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        Print Name of Selling Stockholder

 
By:
 
 
 
         

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        Name:            

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        Title:            

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            (if applicable)
 
 
SELLING STOCKHOLDER

 

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        Print Name of Selling Stockholder

 
By:
 
 
 
         

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        Name:            

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        Title:            

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            (if applicable)
 
 
SELLING STOCKHOLDER

 

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        Print Name of Selling Stockholder

26

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By:
 
 
 
         

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        Name:            

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        Title:            

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            (if applicable)
 
 
SELLING STOCKHOLDER

 

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        Print Name of Selling Stockholder

 
By:
 
 
 
         

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        Name:            

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        Title:            

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            (if applicable)

Confirmed:
 
 

CIBC WORLD MARKETS CORP.
UBS WARBURG LLC
LEERINK SWANN & COMPANY

Acting severally on behalf of itself
and as representative of the several
Underwriters named in Schedule I annexed
hereto.

 

 
 
 
By:
 
CIBC WORLD MARKETS CORP.
 
 

 
 
 
By:
 
 
 
 
 
             

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                Title:                        

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27

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SCHEDULE I

Name

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  Number of
Firm Shares to
Be Purchased
From the Company

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CIBC World Markets Corp.   1,112,500 UBS Warburg LLC   822,500 Leerink Swann &
Company   235,000 Adams, Harkness & Hill, Inc.   75,000 A.G. Edwards & Sons,
Inc.   75,000    

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TOTAL   2,320,000

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SCHEDULE II

Selling Stockholder

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  Number of
Firm Shares to
Be Sold
By Each of the
Selling Stockholders

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L. Michael Cutrer   60,000 Alan I. Edrick   30,000 Dr. Allen M. Green   30,000
Irwin J. Gruverman   50,000 Michael C. Lee   10,000    

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Total   180,000

Underwriters

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  Number of
Firm Shares to
Be Purchased
From the
Selling Stockholders

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CIBC World Markets Corp.
 
180,000    

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Total   180,000

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QuickLinks

2,500,000 Shares NORTH AMERICAN SCIENTIFIC, INC. Common Stock UNDERWRITING
AGREEMENT