DoubleClick Inc.

                  4.75% Convertible Subordinated Notes due 2006

                             REGISTRATION AGREEMENT

                               New York, New York
                                 March 22, 1999

Salomon Smith Barney Inc.
BT Alex. Brown Incorporated
Donaldson, Lufkin & Jenrette Securities Corporation

As Representatives of the Initial Purchasers Named in
  Schedule I to the Purchase Agreement (as defined below)
388 Greenwich Street
New York, New York 10013

Ladies and Gentlemen:

      DoubleClick Inc., a Delaware corporation (the "Company"), proposes to
issue and sell (such issuance and sale, the "Initial Placement") to the several
parties named in Schedule I to the Purchase Agreement (the "Initial Purchasers")
for whom you (the "Representatives") are acting as representatives, upon the
terms set forth in a purchase agreement dated March 17, 1999 (the "Purchase
Agreement"), $200,000,000 aggregate principal amount (plus up to an additional
$50,000,000 aggregate principal amount to cover over-allotments, if any) of its
4.75% Convertible Subordinated Notes due 2006 (the "Securities"). The Securities
will be convertible into shares of common stock, par value $.001 per share, of
the Company at the conversion price set forth in the Offering Memorandum (as
defined herein), as the same may be adjusted from time to time pursuant to the
Indenture referred to below. As an inducement to you to enter into the Purchase
Agreement and in satisfaction of a condition to your obligations thereunder, the
Company agrees with you, (i) for your benefit and (ii) for the benefit of the
holders from time to time of the Securities and the Common Stock issuable upon
conversion of the Securities (including you), as follows:

1. Definitions. Capitalized terms used herein without definition shall have the
respective meanings set forth in the Purchase Agreement. As used in this
Agreement, the following capitalized terms shall have the following meanings:

      "Act" means the Securities Act of 1933, as amended, and the rules and
regulations of the SEC promulgated thereunder.

      "Affiliate" of any specified person means any other person, directly or
indirectly, controlling or controlled by or under direct or indirect common
control with such specified person. For the purposes of this definition,
"control" (including, with correlative meanings, the terms "controlling",
"controlled by" and "under common control with"), as used with respect to any
person, shall mean the possession, directly or indirectly, of the power to
direct or cause the direction of the management or policies of such person,
whether through the ownership of voting securities or by agreement or otherwise.

      "Business Day" has the meaning set forth in the Indenture.

      "Closing Date" means March 22, 1999.

      "Common Stock" means the common stock, par value $.001 per share, of the
Company, as it exists on the date of this Agreement and any other shares of
capital stock or other securities of the Company into which such Common Stock
may be reclassified or changed, together with any and all other securities which
may from time to time be issuable upon conversion of Securities.

      "Damages Payment Date" means, with respect to the Securities or the Common
Stock issuable upon conversion thereof, as applicable, each Interest Payment
Date; and in the event that any Security, or portion thereof, is called for
redemption or surrendered for purchase by the Company and not withdrawn pursuant
to a Designated Event Offer (as defined in the Indenture), the relevant
redemption date or Designated Event Payment Date (as defined in the Indenture),
as the case may be, shall also be a Damages Payment Date with respect to such
Security, or portion thereof, unless the Indenture provides that accrued and
unpaid interest on the Security (or portion thereof) to be redeemed or
repurchased, as the case may be, is to be paid to the person who was the Holder
thereof on a record date prior to such redemption date or Designated Event
Payment Date, as the case may be, in which case the Damages Payment Date shall
be the date on which interest is payable to such Record Holder.

      "Default Rate" has the meaning set forth in the Indenture.

      "DTC" has the meaning set forth in Section 3(k) hereof.

      "Exchange Act" means the Securities Exchange Act of 1934, as amended, and
the rules and regulations of the SEC promulgated thereunder.

      "Final Maturity Date" means March 15, 2006.

      "Holder" means a person who is a holder or beneficial owner (including the
Initial Purchasers) of any Securities or shares of Common Stock issued upon
conversion of Securities; provided that, unless otherwise expressly stated
herein, only registered
<PAGE>

holders of Securities or Common Stock issued on conversion thereof shall be
counted for purposes of calculating any proportion of holders entitled to take
any action or give notice pursuant to this Agreement.

      "Indenture" means the Indenture relating to the Securities dated as of
March 22, 1999, between the Company and The Bank of New York, as trustee, as the
same may be amended from time to time in accordance with the terms thereof.

      "Initial Placement" has the meaning set forth in the preamble hereto.

      "Initial Purchasers" has the meaning set forth in the preamble hereto.

      "Interest Payment Date" shall mean each March 15and September 15.

      "Liquidated Damages" has the meaning set forth in Section 2(e) hereof.

      "Majority Holders" means the Holders of a majority of the then outstanding
aggregate principal amount of Securities registered under a Shelf Registration
Statement; provided that Holders of Common Stock issued upon conversion of
Securities shall be deemed to be Holders of the aggregate principal amount of
Securities from which such Common Stock was converted; and provided, further,
that Securities or Common Stock which have been sold or otherwise transferred
pursuant to the Shelf Registration Statement shall not be included in the
calculation of Majority Holders.

      "Majority Underwriting Holders" means, with respect to any Underwritten
Offering, the Holders of a majority of the then outstanding aggregate principal
amount of Securities registered under any Shelf Registration Statement whose
Securities are or are to be included in such Underwritten Offering; provided
that Holders of Common Stock issued upon conversion of Securities should be
deemed to be Holders of the aggregate principal amount of Securities from which
such Common Stock was converted.

      "Managing Underwriters" means the Underwriter or Underwriters that shall
administer an Underwritten Offering.

      "NASD" has the meaning set forth in Section 3(i) hereof.

      "Notice and Questionnaire" means a Notice of Registration Statement and
Selling Securityholder Questionnaire substantially in the form of Exhibit A
hereto.

      "Offering Memorandum" means the Final Memorandum as defined in the
Purchase Agreement.

      "Person" and "person" have the meaning set forth in the Indenture.

      "Prospectus" means the prospectus included in any Shelf Registration
Statement (including, without limitation, a prospectus that discloses
information previously omitted from a prospectus filed as part of an effective
registration statement in reliance upon Rule 430A under the Act), as amended or
supplemented by any prospectus supplement, with respect to the terms of the
offering of any portion of the Securities or Common Stock issuable upon
conversion thereof covered by such Shelf Registration Statement, and all
amendments and supplements to such prospectus, including all documents
incorporated or deemed to be incorporated by reference in such prospectus.

      "Purchase Agreement" has the meaning set forth in the preamble hereto.

      "Record Holder" means (i) with respect to any Damages Payment Date which
occurs on an Interest Payment Date, each person who is registered on the books
of the registrar as the holder of Securities at the close of business on the
record date with respect to such Interest Payment Date and (ii) with respect to
any Damages Payment Date relating to the Common Stock issued upon conversion
thereof, each person who is a holder of record of such Common Stock fifteen days
prior to the Damages Payment Date.

      "Registration Default" has the meaning set forth in Section 2(e) hereof.
<PAGE>

      "Representatives" has the meaning set forth in the preamble thereto.

      "Rule 144" means Rule 144 (or any successor provision) under the Act.

      "SEC" means the Securities and Exchange Commission.

      "Securities" has the meaning set forth in the preamble hereto.

      "Shelf Registration" means a registration effected pursuant to Section 2
hereof.

      "Shelf Registration Period" has the meaning set forth in Section 2(c)
hereof.

      "Shelf Registration Statement" means a "shelf" registration statement of
the Company pursuant to the provisions of Section 2 hereof which covers all of
the Securities and the Common Stock issuable upon conversion thereof, as
applicable, on Form S-3 or on another appropriate form for an offering to be
made on a delayed or continuous basis pursuant to Rule 415 under the Act, or any
similar rule that may be adopted by the SEC, and all amendments and supplements
to such registration statement, including post-effective amendments, in each
case including the Prospectus contained therein, all exhibits thereto and all
documents incorporated or deemed to be incorporated by reference therein.

      "Stock Split" has the meaning set forth in the Indenture.

      "Suspension Period" has the meaning set forth in Section 2(d) hereof.

      "Transfer Restricted Securities" means each Security and each share of
Common Stock issued upon conversion thereof until the earlier of (A) date on
which such Security or share of Common Stock, as the case may be, (i) has been
transferred pursuant to the Shelf Registration Statement or another registration
statement covering such Security or share of Common Stock which has been filed
with the SEC pursuant to the Act, in either case after such registration
statement has become effective and while such registration statement is
effective under the Act, (ii) has been transferred pursuant to Rule 144 under
the Act (or any similar provision then in force), or (iii) may be sold or
transferred pursuant to Rule 144(k) under the Act (or any successor provision
then in force), or (B) that is the second anniversary of the Closing Date or, if
later, the second anniversary of the last date on which any Securities are
issued upon exercise of the Initial Purchasers' over-allotment option.

      "Trustee" means the trustee with respect to the Securities under the
Indenture.

      "Underwriter" means any underwriter of Securities or Common Stock issuable
upon conversion thereof in connection with an offering thereof under a Shelf
Registration Statement.

      "Underwritten Offering" means an offering in which the Securities or
Common Stock issued upon conversion thereof are sold to an Underwriter or with
the assistance of an Underwriter for reoffering to the public.

      All references in this Agreement to financial statements and schedules and
other information which is "contained", "included", or "stated" in the Shelf
Registration Statement, any preliminary Prospectus or Prospectus (and all other
references of like import) shall be deemed to mean and include all such
financial statements and schedules and other information which is incorporated
or deemed to be incorporated by reference in such Shelf Registration Statement,
preliminary Prospectus or Prospectus, as the case may be; and all references in
this Agreement to amendments or supplements to the Shelf Registration Statement,
any preliminary Prospectus or Prospectus shall be deemed to mean and include the
filing of any document under the Exchange Act, after the date of such Shelf
Registration Statement, preliminary Prospectus or Prospectus, as the case may
be, which is incorporated or deemed to be incorporated by reference therein.

2. Shelf Registration Statement.

(a) The Company shall prepare and, not later than 60 days following the Closing
Date, shall file with the SEC a Shelf Registration Statement with respect to
resales of the Securities and the Common Stock issuable upon conversion thereof
by the Holders from time to time in accordance with the methods of distribution
elected by such Holders and set forth in such Shelf Registration Statement and
thereafter shall use its reasonable best efforts to cause such Shelf
Registration Statement to be declared effective under the Act within 150 days
after the Closing Date;
<PAGE>

provided that if any Securities are issued upon exercise of the over-allotment
option granted to the Initial Purchasers in the Purchase Agreement and the date
on which such Securities are issued occurs after the Closing Date, the Company
will take such steps, prior to the effective date of the Shelf Registration
Statement, to ensure that such Securities and Common Stock issuable upon
conversion thereof are included in the Shelf Registration Statement on the same
terms as the Securities issued on the Closing Date. The Company shall supplement
or amend the Shelf Registration Statement if required by the rules, regulations
or instructions applicable to the registration form used by the Company for the
Shelf Registration Statement, if required by the Act, the Exchange Act or the
SEC.

            (b) (1) Not less than 30 calendar days prior to the effectiveness of
      the Shelf Registration Statement, the Company shall mail the Notice and
      Questionnaire to the Holders of Securities and Common Stock issued upon
      conversion thereof. No Holder shall be entitled to be named as a selling
      securityholder in the Shelf Registration Statement, and no Holder shall be
      entitled to use the Prospectus forming a part thereof for resales of
      Securities or Common Stock issued upon conversion thereof at any time,
      unless such Holder has returned a completed and signed Notice and
      Questionnaire to the Company by the deadline for responses set forth
      therein; provided, however, that Holders of Securities or Common Stock
      issued upon conversion thereof shall have at least 20 calendar days from
      the date on which the Notice and Questionnaire is first mailed to such
      Holders to return a completed and signed Notice and Questionnaire to the
      Company.

            (2) After the Shelf Registration Statement has become effective, the
      Company shall, upon the request of any Holder of Securities or Common
      Stock issued or issuable upon conversion thereof that has not returned a
      completed Notice and Questionnaire, promptly send a Notice and
      Questionnaire to such Holder. The Company shall not be required to take
      any action to name such Holder as a selling securityholder in the Shelf
      Registration Statement or to enable such Holder to use the Prospectus
      forming a part thereof for resales of Securities or Common Stock issued or
      issuable upon conversion thereof until such Holder has returned a
      completed and signed Notice and Questionnaire to the Company, whereupon
      the Company will be required to take such action.

(c) The Company shall keep the Shelf Registration Statement continuously
effective under the Act in order to permit the Prospectus forming part thereof
to be usable by all Holders until the earliest of (i) the second anniversary of
the Closing Date or, if later, the second anniversary of the last date on which
any Securities are issued upon exercise of the Initial Purchasers'
over-allotment option, (ii) the date on which all the Securities and Common
Stock issued or issuable upon conversion thereof may be sold by non-affiliates
("affiliates" for such purpose having the meaning set forth in Rule 144) of the
Company pursuant to paragraph (k) of Rule 144 (or any successor provision)
promulgated by the SEC under the Act, (iii) the date as of which all the
Securities and Common Stock issued or issuable upon conversion thereof have been
transferred pursuant to Rule 144 under the Securities Act (or any similar
provision then in force) and (iv) such date as of which all the Securities and
the Common Stock issued or issuable upon conversion thereof have been sold
pursuant to the Shelf Registration Statement (in any such case, such period
being called the "Shelf Registration Period"). The Company will, subject to
Section 2(d), prepare and file with the SEC such amendments and post-effective
amendments to the Shelf Registration Statement as may be necessary to keep the
Shelf Registration Statement continuously effective for the Shelf Registration
Period; subject to Section 2(d), cause the related Prospectus to be supplemented
by any required supplement, and as so supplemented to be filed pursuant to Rule
424 (or any similar provisions then in force) under the Act; and, comply in all
material respects with the provisions of the Act with respect to the disposition
of all securities covered by the Shelf Registration Statement during the
<PAGE>

applicable period in accordance with the intended methods of disposition by the
sellers thereof set forth in such Shelf Registration Statement as so amended or
such Prospectus as so supplemented.

(d) The Company may suspend the use of the Prospectus for a period not to exceed
30 days in any three-month period or for three periods not to exceed an
aggregate of 90 days in any twelve-month period (the "Suspension Period") for
valid business reasons, to be determined by the Company in its sole reasonable
judgment (not including avoidance of the Company's obligations hereunder),
including, without limitation, the acquisition or divestiture of assets, public
filings with the SEC, pending corporate developments and similar events;
provided that the Company promptly thereafter complies with the requirements of
Section 3(j) hereof, if applicable; provided, that the existence of a Suspension
Period will not prevent the occurrence of a Registration Default or otherwise
limit the obligation of the Company to pay Liquidated Damages. The Company shall
provide notice to the Holders of a Suspension Period as required under Section
3(c)(1)(iv) hereof.

(e) If (i) the Shelf Registration Statement is not filed with the SEC on or
prior to 60 days after the Closing Date, (ii) the Shelf Registration Statement
has not been declared effective by the SEC within 150 days after the Closing
Date, or (iii) the Shelf Registration Statement is filed and declared effective
but shall thereafter cease to be effective (without being succeeded immediately
by a replacement shelf registration statement filed and declared effective) or
usable (including as a result of a Suspension Period) for the offer and sale of
Transfer Restricted Securities for a period of time (including any Suspension
Period) which shall exceed 60 days in the aggregate in any twelve-month period
during the period beginning on the Closing Date and ending on the second
anniversary of the Closing Date or, if later, the second anniversary of the last
date on which any Securities are issued upon exercise of the Initial Purchasers'
over-allotment option (each such event referred to in clauses (i) through (iii),
a "Registration Default"), the Company will pay liquidated damages ("Liquidated
Damages") to each Holder of Transfer Restricted Securities who has complied with
such Holder's obligations under this Agreement. The amount of Liquidated Damages
payable during any period in which a Registration Default has occurred and is
continuing is the amount which is equal to one-quarter of one percent (25 basis
points) per annum per $1,000 principal amount of Securities and $2.50 per annum
per 6.06061 shares of Common Stock (subject to adjustment in the event of a
stock split, stock recombination, stock dividend and the like) constituting
Transfer Restricted Securities for the first 90 days during which a Registration
Default has occurred and is continuing and one-half of one percent (50 basis
points) per annum per $1,000 principal amount of Securities and $5.00 per annum
per 6.06061 shares of Common Stock (subject to adjustment as set forth above)
constituting Transfer Restricted Securities for any additional days during which
a Registration Default has occurred and is continuing; provided that, the
Company hereby agrees that, upon the occurrence of the Stock Split (which it is
currently contemplated will occur on April 2, 1999), the Liquidated Damages
payable in respect of Common Stock shall be automatically adjusted to $2.50 per
annum per 12.12121 shares of Common Stock for the first such 90 days during
which a Registration Default has occurred and is continuing and $5.00 per annum
per 12.12121 shares of Common Stock for any additional days during which such
Registration Default has occurred and is continuing (in each case subject to
further adjustment from time to time in the event of a stock split, stock
recombination, stock dividend and the like), it being understood that all
calculations pursuant to this and the preceding sentence shall be carried out to
five decimals. Following the cure of all Registration Defaults, Liquidated
Damages will cease to accrue with respect to such Registration Default. All
accrued Liquidated Damages shall be paid by wire transfer of immediately
available funds or by federal funds check by the Company on each Damages Payment
Date and Liquidated Damages will be calculated on the basis of a 360-day year
consisting of twelve 30-day months. In the event that any Liquidated Damages are
not paid when due, then to the extent permitted by law, such overdue Liquidated
Damages, if any, shall bear interest until paid at the Default Rate, compounded
semi-annually. The parties hereto agree that the Liquidated Damages provided for
in this Section 2(e) constitute a reasonable estimate of the damages that may be
incurred by Holders by reason of a Registration Default.

(f) All of the Company's obligations (including, without limitation, the
obligation to pay Liquidated Damages) set forth in the preceding paragraph which
are outstanding or exist with respect to any Transfer Restricted Security at the
time such security ceases to be a Transfer Restricted Security shall survive
until such time as all such obligations with respect to such security shall have
been satisfied in full.

(g) Immediately upon the occurrence or the termination of a Registration
Default, the Company shall give the Trustee, in the case of notice with respect
to the Securities, and the transfer and paying agent for the Common Stock, in
the case of notice with respect to Common Stock issued or issuable upon
conversion thereof, notice of such commencement or termination, of the
obligation to pay Liquidated Damages with regard to the Securities and Common
Stock and the amount thereof and of the event giving rise to such commencement
or termination (such notice to be contained in an Officers' Certificate (as such
term is defined in the Indenture)), and prior to receipt of such Officer'
Certificate the Trustee and such transfer and paying agent shall be entitled to
assume that no such commencement or termination has occurred, as the case may
be.
<PAGE>

(h) All Securities which are redeemed, purchased or otherwise acquired by the
Company or any of its subsidiaries or affiliates (as defined in Rule 144 (or any
successor provision) under the Act) prior to the Final Maturity Date shall be
delivered to the Trustee for cancellation and the Company may not hold or resell
such Securities or issue any new Securities to replace any such Securities or
any Securities that any Holder has converted pursuant to the Indenture. All
shares of Common Stock issued upon conversion of the Securities which are
repurchased or otherwise acquired by the Company or any of its subsidiaries or
affiliates (as defined in Rule 144 (or any successor provision) under the Act)
at any time while such shares are "restricted securities" within the meaning of
Rule 144 shall not be resold or otherwise transferred except pursuant to a
registration statement which has been declared effective under the Act.

3. Registration Procedures. In connection with any Shelf Registration Statement,
the following provisions shall apply:

(a) The Company shall furnish to you, prior to the filing thereof with the SEC,
a copy of any Shelf Registration Statement, and each amendment thereof
(excluding amendments caused by the filing by the Company with the SEC of a
report required by the Exchange Act), a copy of any Prospectus, and each
amendment or supplement, if any, to the Prospectus included therein and shall
use its best efforts to reflect in each such document, when so filed with the
SEC, such comments as Salomon Smith Barney Inc. reasonably may propose. Salomon
Smith Barney Inc. shall promptly furnish to the Company any comments it may have
to such documents mentioned in the foregoing sentence.

(b) The Company shall ensure that (i) any Shelf Registration Statement and any
amendment thereto and any Prospectus forming part thereof and any amendment or
supplement thereto comply in all material respects with the Act and the rules
and regulations thereunder, (ii) any Shelf Registration Statement and any
amendment thereto does not, when it becomes effective, contain an untrue
statement of a material fact or omit to state a material fact required to be
stated therein or necessary to make the statements therein not misleading and
(iii) any Prospectus forming part of any Shelf Registration Statement, and any
amendment or supplement to such Prospectus, does not include an untrue statement
of a material fact or omit to state a material fact necessary in order to make
the statements therein, in light of the circumstances under which they were
made, not misleading; provided that the Company makes no representation or
agreement with respect to information with respect to you, any Underwriter or
any Holder required to be included in any Shelf Registration or Prospectus
pursuant to the Act or the rules and regulations thereunder and which
information is included therein in reliance upon and in conformity with
information furnished to the Company in writing by you, any Underwriter or any
such Holder.

            (c) (1) The Company, as promptly as reasonably practicable, shall
      advise you and each Holder that has returned a completed and signed Notice
      and Questionnaire to the Company and, if requested by you or any such
      Holder, confirm such advice in writing:

                  (i) when a Shelf Registration Statement and any amendment
            thereto has been filed with the SEC and when the Shelf Registration
            Statement or any post-effective amendment thereto has become
            effective;

                  (ii) of any request by the SEC for amendments or supplements
            to the Shelf Registration Statement or the Prospectus or for
            additional information;

                  (iii) of the determination by the Company that a
            post-effective amendment to the Shelf Registration Statement would
            be appropriate; and

                  (iv) of the commencement or termination of any Suspension
            Period.
<PAGE>

            (2) The Company shall advise you and each Holder that has returned a
      completed and signed Notice and Questionnaire to the Company and, if
      requested by you or any such Holder, confirm such advice in writing:

                  (i) of the issuance by the SEC of any stop order suspending
            the effectiveness of the Shelf Registration Statement or the
            initiation of any proceedings for that purpose;

                  (ii) of the receipt by the Company of any notification with
            respect to the suspension of the qualification of the Securities
            included in any Shelf Registration Statement for sale in any
            jurisdiction or the initiation or threat of any proceeding for such
            purpose; and

                  (iii) of the suspension of the use of the Prospectus pursuant
            to Section 2(d) hereof or of the happening of any event that
            requires the making of any changes in the Shelf Registration
            Statement or the Prospectus so that, as of such date, the statements
            therein are not misleading and the Shelf Registration Statement or
            the Prospectus, as the case may be, does not include an untrue
            statement of a material fact or omit to state a material fact
            required to be stated therein or necessary to make the statements
            therein (in the case of the Prospectus, in light of the
            circumstances under which they were made) not misleading (which
            advice shall be accompanied by an instruction to suspend the use of
            the Prospectus until the requisite changes have been made).

(d) The Company shall use its reasonable best efforts to obtain the withdrawal
of any order suspending the effectiveness of any Shelf Registration Statement or
the lifting of any suspension of the qualification (or exemption from
qualification) of any of the Securities for offer or sale in any jurisdiction at
the earliest possible time.

(e) The Company shall furnish to each Holder of Securities and the Common Stock
issued upon conversion thereof included within the coverage of any Shelf
Registration Statement, without charge, at least one copy of such Shelf
Registration Statement and any post-effective amendment thereto, including
financial statements and schedules, and, if the Holder so requests in writing,
all exhibits (including those incorporated by reference).

(f) The Company shall, during the Shelf Registration Period, deliver to each
Holder of Securities or the Common Stock issued upon conversion thereof included
within the coverage of any Shelf Registration Statement, without charge, as many
copies of the Prospectus (including each preliminary Prospectus) included in
such Shelf Registration Statement and any amendment or supplement thereto as
such Holder may reasonably request; and, except during the continuance of any
Suspension Period, the Company consents to the use of the Prospectus or any
amendment or supplement thereto by each of the selling Holders in connection
with the offering and sale of the Securities or the Common Stock issued upon
conversion thereof covered by the Prospectus or any amendment or supplement
thereto.

(g) Prior to any offering of Securities or the Common Stock issued upon
conversion thereof pursuant to any Shelf
<PAGE>

Registration Statement, the Company shall register or qualify or cooperate with
the Holders of Securities and the Common Stock issued upon conversion thereof
included therein and their respective counsel in connection with the
registration or qualification (or exemption from such registration or
qualification) of such Securities or Common Stock for offer and sale, as the
case may be, under the securities or blue sky laws of such jurisdictions as any
such Holders reasonably request in writing and do any and all other acts or
things necessary or advisable to enable the offer and sale in such jurisdictions
of the Securities and the Common Stock issued upon conversion thereof covered by
such Shelf Registration Statement; provided, however, that the Company will not
be required to (A) qualify generally to do business in any jurisdiction where it
is not then so qualified or to (B) take any action which would subject it to
general service of process or to taxation in any such jurisdiction where it is
not then so subject.

(h) The Company shall cooperate with the Holders to facilitate the timely
preparation and delivery of certificates representing Securities or the Common
Stock issued upon conversion thereof to be sold pursuant to any Shelf
Registration Statement free of any restrictive legends and in such denominations
and registered in such names as Holders may request prior to sales of Securities
or the Common Stock issued upon conversion thereof pursuant to such Shelf
Registration Statement.

(i) Subject to the exceptions contained in (A) and (B) of subsection (g) hereof,
the Company shall use its best efforts to cause the Securities and Common Stock
issued upon conversion thereof covered by the applicable Shelf Registration
Statement to be registered with or approved by such other federal, state and
local governmental agencies or authorities, and self-regulatory organizations in
the United States as may be necessary to enable the Holders to consummate the
disposition of such Securities and Common Stock issued upon conversion thereof
as contemplated by the Shelf Registration Statement; without limitation to the
foregoing, the Company shall make all filings and provide all such information
as may be required by the National Association of Securities Dealers, Inc. (the
"NASD") in connection with the offering under the Shelf Registration Statement
of the Securities and Common Stock issued upon conversion thereof (including,
without limitation, such as may be required by NASD Rule 2710 or 2720), and
shall cooperate with each Holder in connection with any filings required to be
made with the NASD by such Holder in that regard.

(j) Upon the occurrence of any event contemplated by paragraph 3(c)(2)(iii)
above and subject to Section 3(a) hereof, the Company shall promptly prepare and
file with the SEC a post-effective amendment to any Shelf Registration Statement
or an amendment or supplement to the related Prospectus or any document
incorporated therein by reference or file a document which is incorporated or
deemed to be incorporated by reference in such Shelf Registration Statement or
Prospectus, as the case may be, so that, as thereafter delivered to purchasers
of the Securities or the Common Stock issued upon conversion thereof included
therein, the Shelf Registration Statement and the Prospectus, in each case as
then amended or supplemented, will not include an 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 (in the case of the Prospectus
in light of the circumstances under which they were made) not misleading and in
the case of a post-effective amendment, use its best efforts to cause it to
become effective as promptly as practicable; provided that the Company's
obligations under this paragraph (j) shall be suspended if the Company has
suspended the use of the Prospectus in accordance with Section 2(d) hereof and
given notice of such suspension to Holders, it being understood that the
Company's obligations under this Subsection (j) shall be automatically
reinstated at the end of such Suspension Period.

(k) The Company shall use its reasonable best efforts to cause The Depository
Trust Company ("DTC") on the first Business Day following the effective date of
any Shelf Registration Statement hereunder or as soon as possible thereafter to
remove (i) from any existing CUSIP number assigned to the Securities any
designation indicating that the Securities are ""restricted securities", which
efforts shall include delivery to DTC of a letter executed by the Company
substantially in the form of Exhibit B hereto and (ii) any other stop or
restriction on DTC's system with respect to the Securities. In the event the
Company is unable to cause DTC to take actions described in the immediately
preceding sentence, the Company shall take such actions as Salomon Smith Barney
Inc. may reasonably request to provide, as soon as practicable, a CUSIP number
for the Securities registered under such Shelf Registration Statement and to
cause such CUSIP number to be assigned to such Securities (or to the maximum
aggregate principal amount of the Securities to which such number may be
assigned). Upon compliance with the foregoing requirements of this Section 3(k),
the Company shall provide the Trustee with global certificates for such
Securities in a form eligible for deposit with DTC.

(l) The Company shall use its best efforts to comply with all applicable rules
and regulations of the SEC and shall make generally available to its security
holders as soon as practicable but in any event not later than 15 months after
(i) the effective date of the applicable Shelf Registration Statement, (ii) the
effective date of each post-effective amendment to any Shelf Registration
Statement, and (iii) the date of each filing by the Company with the SEC of an
Annual Report on Form 10-K that is incorporated by reference or deemed to be
incorporated by
<PAGE>

reference in the Shelf Registration Statement, an earnings statement satisfying
the provisions of Section II(a) of the Act and Rule 158 promulgated by the SEC
thereunder.

(m) The Company shall use its best efforts to cause the Indenture to be
qualified under the TIA (as defined in the Indenture) in a timely manner.

(n) The Company shall cause all Common Stock issued or issuable upon conversion
of the Securities to be listed on each securities exchange or quotation system
on which the Common Stock is then listed no later than the date the applicable
Shelf Registration Statement is declared effective and, in connection therewith,
to make such filings as may be required under the Exchange Act and to have such
filings declared effective as and when required thereunder.

(o) The Company may require each Holder of Securities or the Common Stock issued
upon conversion thereof to be sold pursuant to any Shelf Registration Statement
to furnish to the Company such information regarding the Holder and the
distribution of such Securities or Common Stock sought by the Notice and
Questionnaire and such additional information as may, from time to time, be
required by the Act and the rules and regulations promulgated thereunder, and
the obligations of the Company to any Holder hereunder shall be expressly
conditioned on the compliance of such Holder with such request.

(p) The Company shall, if reasonably requested, use its best efforts to promptly
incorporate in a Prospectus supplement or post-effective amendment to a Shelf
Registration Statement (i) such information as the Majority Holders provide or,
if the Securities or Common Stock are being sold in an Underwritten Offering, as
the Managing Underwriters or the Majority Underwriting Holders reasonably agree
should be included therein and provide to the Company in writing for inclusion
in the Shelf Registration Statement or Prospectus, and (ii) such information as
a Holder may provide from time to time to the Company in writing for inclusion
in a Prospectus or any Shelf Registration Statement concerning such Holder and
the distribution of such Holder's Securities and Common Stock and, in either
case, shall make all required filings of such Prospectus supplement or
post-effective amendment as soon as practicable after being notified in writing
of the matters to be incorporated in such Prospectus supplement or
post-effective amendment, provided that the Company shall not be required to
take any action under this Section 3(p) that is not, in the reasonable opinion
of counsel for the Company, in compliance with applicable law.

(q) The Company shall enter into such customary agreements (including
underwriting agreements) and take all other appropriate actions as may be
reasonably requested in order to expedite or facilitate the registration or the
disposition of the Securities or the Common Stock issued or issuable upon
conversion thereof, and in connection therewith, if an underwriting agreement is
entered into, cause the same to contain indemnification and contribution
provisions and procedures no less favorable than those set forth in Section 5
(or such other reasonable and customary provisions and procedures acceptable to
the Majority Underwriting Holders and the Managing Underwriters, if any, with
respect to all parties to be indemnified pursuant to Section 5). The plan of
distribution in the Shelf Registration Statement and the Prospectus included
therein shall permit resales of the Securities or Common Stock issuable upon
conversion thereof to be made by selling security holders through underwriters,
brokers and dealers, and shall also include such other information as Salomon
Smith Barney Inc. may reasonably request.

(r) The Company shall (i) make reasonably available for inspection by the
Holders of Securities and the Common Stock issued upon conversion thereof
registered or to be registered under a Shelf Registration Statement, any
Underwriter participating in any disposition pursuant to such Shelf Registration
Statement, and any attorney, accountant or other agent retained by the Holders
or any such Underwriter all relevant financial and other records, pertinent
corporate documents and properties of the Company and its subsidiaries as is
customary for due diligence examinations in connection with public offerings;
(ii) cause the Company's officers, directors and employees to supply all
relevant information reasonably requested by the Holders or any such
Underwriter, attorney, accountant or agent in connection with any such Shelf
Registration Statement as is customary for similar due diligence examinations;
provided, however, that any information that is designated in writing by the
Company, in its sole discretion, as confidential at the time of delivery of such
information shall be kept confidential by the Holders or any such Underwriter,
attorney, accountant or agent, unless disclosure thereof is made in connection
with a court, administrative or regulatory proceeding or required by law, or
such information has become available to the public generally through the
Company or through a third party without an accompanying obligation of
confidentiality; provided, further, that if the foregoing inspection and
information gathering specified in subsections (i) and (ii) would, in the
Company's reasonable judgment, disrupt the Company's conduct of business, such
inspections and information gathering shall be coordinated on behalf of the
Holders and the other parties entitled thereto by one counsel designated by or
on
<PAGE>

behalf of the Majority Holders (or, in the case of an Underwritten Offering, the
Majority Underwriting Holders and the Managing Underwriters); (iii) make such
representations and warranties to the Holders of Securities and the Common Stock
issued upon conversion thereof registered thereunder and the Underwriters, if
any, in form, substance and scope as are customarily made by issuers to
Underwriters and covering matters including, but not limited to, those set forth
in the Purchase Agreement; (iv) obtain opinions of counsel to the Company and
updates thereof (which counsel and opinions, in form, scope and substance, shall
be reasonably satisfactory to the Managing Underwriters, if any) addressed to
each selling Holder and the Underwriters, if any, covering such matters as are
customarily covered in opinions requested in public offerings; (v) obtain "cold
comfort" letters and updates thereof from the independent certified public
accountants of the Company (and, if necessary, any other independent certified
public accountants of any subsidiary of the Company or of any business acquired
by the Company for which financial statements and financial data are, or are
required to be, included in the Shelf Registration Statement), addressed to each
selling Holder of Securities and Common Stock issued upon conversion thereof
registered thereunder (provided such Holder furnishes the accountants with such
representations as the accountants customarily require in similar situations)
and the Underwriters, if any, in customary form and covering matters of the type
customarily covered in "cold comfort" letters in connection with primary
underwritten offerings; and (vi) deliver such documents and certificates as may
be reasonably requested by the Majority Holders or, in the case of an
Underwritten Offering, the Majority Underwriting Holders, and the Managing
Underwriters, if any, including those to evidence compliance with Section 3(j)
and with any customary conditions contained in the underwriting agreement or
other agreement entered into by the Company. The foregoing actions set forth in
clauses (iii), (iv), (v) and (vi) of this Section 3(r) shall be performed at (A)
the effectiveness of such Shelf Registration Statement and each post-effective
amendment thereto and (B) each closing under any underwriting or similar
agreement as and to the extent required thereunder.

(s) Each Holder agrees that, upon receipt of notice of the happening of an event
described in Sections 3(c)(1)(ii) through and including 3(c)(1)(iv) and Sections
3(c)(2)(i) through and including 3(c)(2)(iii), each Holder shall forthwith
discontinue (and shall cause its agents and representatives to discontinue)
disposition of the Securities and the Common Stock issuable upon conversion
thereof and will not resume disposition of such Securities or the Common Stock
until such Holder has received copies of an amended or supplemented Prospectus
contemplated by Section 3(j) hereof, or until such Holder is advised in writing
by the Company that the use of the Prospectus may be resumed or that the
relevant Suspension Period has been terminated, as the case may be, provided
that, the foregoing shall not prevent the sale, transfer or other disposition of
Securities or Common Stock issuable upon conversion thereof by a Holder in a
transaction which is exempt from, or not subject to, the registration
requirements of the Act, so long as such Holder does not and is not required to
deliver the applicable Prospectus or Shelf Registration Statement in connection
with such sale, transfer or other disposition, as the case may be; and provided,
further, that the provisions of this paragraph (s) shall not prevent the
occurrence of a Registration Default or otherwise limit the obligation of the
Company to pay Liquidated Damages.

(t) Anything herein to contrary notwithstanding, the Company will not be
required to pay the costs and expenses of, or to participate in the marketing or
"road show" presentations of, more than one Underwritten Offering initiated at
the request of the Holders of Securities or shares of Common Stock issued or
issuable upon conversion thereof, or to effect more than one Underwritten
Offering at the request of such Holders. The Company will not be required to pay
the costs and expenses of, or to participate in the marketing or "road show"
presentations of, an Underwritten Offering unless Holders of at least the
Minimum Amount (as defined below) of Securities and/or Common Stock issued or
issuable on conversion thereof have requested that such Securities and/or shares
of Common Stock be included in such an Underwritten Offering. For purposes of
this Agreement, the "Minimum Amount" means 25% of the aggregate principal amount
of Securities originally issued under the Indenture; provided that, for purposes
of computing the Minimum Amount, Holders of Common Stock issued upon conversion
of Securities shall be deemed to be holders of the aggregate principal amount of
Securities which were converted into those shares of Common Stock. Only Holders
of Securities or shares of Common Stock issued or issuable upon conversion
thereof which are Transfer Restricted Securities shall be entitled to include
such Securities or shares of Common Stock in an Underwritten Offering and only
Transfer Restricted Securities shall be included in the computation of the
Minimum Amount. The Underwritten Offering initiated by Holders as aforesaid
shall include both Securities and Common Stock if so requested by the Holders.
Upon receipt by the Company, from Holders of at least the Minimum Amount of
Securities and/or Common Stock issued or issuable upon conversion thereof, of a
request for an Underwritten Offering, the Company will, within 10 days
thereafter, mail notice to all Holders of Securities and shares of Common Stock
issued upon conversion/hereof stating that: (i) the Company has received a
request from the Holders of the requisite amount of Securities and/or Common
Stock issued or issuable on conversion thereof to effect an Underwritten
Offering on behalf of such Holders; (ii) under the terms of this Agreement, all
Holders of Securities and shares of Common Stock issued or issuable upon
conversion thereof which are Transfer Restricted Securities may include their
Securities and shares of Common Stock in such Underwritten Offering, subject to
the terms and conditions set forth in this Agreement and subject to the right of
the Managing Underwriters to reduce, in light of market conditions and other
similar factors, the aggregate principal amount of Securities and number of
shares of Common Stock included in such Underwritten Offering; (iii) all Holders
electing to include Securities or shares of Common Stock in such
<PAGE>

Underwritten Offering must notify the Company in writing of such election (the
"Election"), and setting forth an address and facsimile number to which such
written elections may be sent and the deadline (which shall be 12:00 midnight on
the 30th calendar day after such notice is mailed to Holders or, if not a
Business Day, the next succeeding Business Day (the "Deadline")) by which such
elections must be received by the Company; and (iv) setting forth such other
instructions as shall be necessary to enable Holders to include their Securities
and shares of Common Stock in such Underwritten Offering. No Holder shall be
entitled to participate in an Underwritten Offering unless such Holder notifies
the Company of such Election by the Deadline. Notwithstanding anything to the
contrary contained herein, if the Managing Underwriters for an Underwritten
Offering to be effected pursuant to this Section 3(t) advise the Holders of the
Securities and shares of the Common Stock to be included in such Underwritten
Offering that, because of aggregate principal amount of Securities and/or number
of shares of Common Stock that such Holders have requested be included in the
Underwritten Offering, the success of the offering would likely be materially
adversely affected by the inclusion of all of the Securities and shares of
Common Stock requested to be included, then the principal amount of Securities
and the number of shares of Common Stock to be offered for the accounts of
Holders shall be reduced pro rata, according to the aggregate principal amount
of Securities and number of shares of Common Stock, respectively, requested for
inclusion by each such Holder, to the extent necessary to reduce the size of the
offering to the size recommended by the Managing Underwriter. Notwithstanding
anything to the contrary contained herein, neither the Company nor any Person,
other than a Holder of Securities or shares of Common Stock issued or issuable
upon conversion thereof and only with respect to its Transfer Restricted
Securities, shall be entitled to include any securities in the Underwritten
Offering.

4. Registration Expenses. The Company shall bear all expenses incurred in
connection with the performance of its obligations under Sections 2 and 3 hereof
and shall reimburse the Holders for the reasonable fees and disbursements of one
firm or counsel designated by the Majority Holders to act as counsel for the
Holders in connection therewith. Notwithstanding the provisions of this Section
4, each Holder shall bear the expense of any broker's commission, agency fee or
Underwriter's discount or commission.

5. Indemnification and Contribution.

            (a) (i) The Company agrees to indemnify and hold harmless each
      Holder of Securities and each Holder of Common Stock issued upon
      conversion thereof covered by any Shelf Registration Statement (including
      the Initial Purchasers), the directors, officers, employees and agents of
      each such Holder and each person who controls any such Holder within the
      meaning of either the Act or the Exchange Act against any and all losses,
      claims, damages or liabilities, joint or several, to which they or any of
      them may become subject under the 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 (or actions in respect thereof)
      arise out of or are based upon any untrue statement or alleged untrue
      statement of a material fact contained in the Shelf Registration Statement
      as originally filed or in any amendment thereof, or in any preliminary
      Prospectus or Prospectus, or in any amendment thereof or supplement
      thereto, or arise out of or are based upon the omission or alleged
      omission to state therein a material fact required to be stated therein or
      necessary to make the statements therein, in the light of the
      circumstances under which they were made, not misleading, and agrees to
      reimburse each such indemnified party, as incurred, for any legal or other
      expenses reasonably incurred by any of them in connection with
      investigating or defending any such loss, claim, damage, liability or
      action;
<PAGE>

      provided, however, that the Company will not be liable in any such case to
      the extent that any such loss, claim, damage or liability arises out of or
      is based upon (A) any such untrue statement or alleged untrue statement or
      omission or alleged omission made therein in reliance upon and in
      conformity with written information furnished to the Company by or on
      behalf of any such Holder or any Initial Purchaser specifically for
      inclusion therein, (B) use of a Shelf Registration Statement or the
      related Prospectus during a period when a stop order has been issued in
      respect of such Shelf Registration or any proceedings for that purpose
      have been initiated or use of a Prospectus when use of such Prospectus has
      been suspended pursuant to Section 2(d) or Section 3(s); provided,
      further, in each case, that Holders received prior notice of such stop
      order, initiation of proceedings or suspension, or (C) if the Holder fails
      to deliver a Prospectus, as then amended or supplemented, provided that
      the Company shall have delivered to such Holder such Prospectus, as then
      amended or supplemented. This indemnity agreement will be in addition to
      any liability which the Company may otherwise have.

            (ii) The Company also agrees to indemnify and to contribute to
      Losses, as provided in Section 5(d), of any Underwriters of Securities or
      Common Stock issued upon conversion thereof registered under a Shelf
      Registration Statement, their officers and directors and each person who
      controls any such Underwriter within the meaning of either the Act or the
      Exchange Act on substantially the same basis as that of the
      indemnification of the Initial Purchasers and the selling Holders provided
      in this Section 5(a) and shall, if requested by any Holder, enter into an
      underwriting agreement reflecting such agreement, as provided in Section
      3(q) hereof. This indemnity agreement will be in addition to any liability
      which the Company may otherwise have.

(b) Each Holder of Securities or Common Stock issued upon conversion thereof
covered by a Shelf Registration Statement (including the Initial Purchasers)
severally and not jointly agrees to indemnify and hold harmless (i) the Company,
(ii) each of its directors, (iii) each of its officers who signs such Shelf
Registration Statement and (iv) each person who controls the Company within the
meaning of either the Act or the Exchange Act to the same extent as the
foregoing indemnity from the Company to each such Holder, but only with
reference to written information relating to such Holder furnished to the
Company by or on behalf of such Holder specifically for inclusion in the
documents referred to in the foregoing indemnity. This indemnity agreement will
be in addition to any liability which any such Holder may otherwise have.

(c) Promptly after receipt by an indemnified party under this Section 5 of
notice of the commencement of any action, such indemnified party will, if a
claim in respect thereof is to be made against the indemnifying party under this
Section 5, notify the indemnifying party in writing of the commencement thereof;
but the failure so to notify the indemnifying party (i) will not relieve it from
liability under paragraph (a) or (b) above unless and to the extent it did not
otherwise learn of such action and such failure results in the forfeiture by the
indemnifying party
<PAGE>

of substantial rights and defenses; and (ii) will not, in any event, relieve the
indemnifying party from any obligations to any indemnified party other than the
indemnification obligation provided in paragraph (a) or (b) above. The
indemnifying party shall be entitled to appoint counsel of the indemnifying
party's choice at the indemnifying party's expense to represent the indemnified
party in any action for which indemnification is sought (in which case the
indemnifying party shall not thereafter be responsible for the fees and expenses
of any separate counsel retained by the indemnified party or parties except as
set forth below); provided, however, that such counsel shall be reasonably
satisfactory to the indemnified party. Notwithstanding the indemnifying party's
election to appoint counsel to represent the indemnified party in an action, the
indemnified party shall have the right to employ separate counsel (including
local counsel), and the indemnifying party shall bear the reasonable fees, costs
and expenses of such separate counsel (and local counsel) if (i) the use of
counsel chosen by the indemnifying party to represent the indemnified party
would present such counsel with a conflict of interest; (ii) the actual or
potential defendants in, or targets of, any such action include both the
indemnified party and the indemnifying party and the indemnified party shall
have reasonably concluded that there may be legal defenses available to it
and/or other indemnified parties which are different from or additional to those
available to the indemnifying party; (iii) the indemnifying party shall not have
employed counsel satisfactory to the indemnified party to represent the
indemnified party within a reasonable time after notice of the institution of
such action; or (iv) the indemnifying party shall authorize the indemnified
party to employ separate counsel at the expense of the indemnifying party.
Notwithstanding the foregoing, the Company shall not, in the connection with any
one action or proceeding or separate but substantially similar or related
actions or proceedings in the same jurisdiction arising out of the same general
allegations or circumstances, be liable for the reasonable fees and expenses of
more than one separate counsel (in addition to one separate local counsel) at
any time for the indemnified parties, which firm or firms (including any local
counsel) shall be designated by Salomon Smith Barney Inc. An indemnifying party
will not, without the prior written consent of the indemnified party, which
consent will not be unreasonably withheld, settle or compromise or consent to
the entry of any judgment with respect to any pending or threatened claim,
action, suit or proceeding in respect of which indemnification or contribution
may be sought hereunder (whether or not the indemnified parties are actual or
potential parties to such claim or action) unless such settlement, compromise or
consent includes an unconditional release of such indemnified party from all
liability arising out of such claim, action, suit or proceeding. The Company
shall not be liable for any losses, claims, damages or liabilities by reason of
any settlement of any action or proceeding effected without the Company's prior
written consent, which consent will not be unreasonably withheld.

(d) In the event that the indemnity provided in paragraph (a) or (b) of this
Section 5 is unavailable to or insufficient to hold harmless an indemnified
party for any reason, then each applicable indemnifying party, in lieu of
indemnifying such indemnified party, shall have an obligation to contribute to
the aggregate losses, claims, damages and liabilities (including legal or other
expenses reasonably incurred in connection with investigating or defending same)
(collectively "Losses"), as incurred, to which such indemnified party may be
subject in such proportion as is appropriate to reflect the relative benefits
received by such indemnifying party, on the one hand, and such indemnified
party, on the other hand, from the Initial Placement and the Shelf Registration
Statement which resulted in such Losses; provided, however, that in no case
shall the Initial Purchasers be responsible, in the aggregate, for any amount in
excess of the purchase discount or commission applicable to the Securities, as
set forth on the cover page of the Offering Memorandum, nor shall any
Underwriter be responsible for any amount in excess of the underwriting discount
or commission applicable to the Securities and Common Stock issued upon
conversion thereof purchased by such Underwriter under the Shelf Registration
Statement which resulted in such Losses. If the allocation provided by the
immediately preceding sentence is unavailable for any reason, the indemnifying
party and the indemnified party shall contribute in such proportion as is
appropriate to reflect not only such relative benefits but also the relative
fault of such indemnifying party, on the one hand, and such indemnified party,
on the other hand, in connection with the statements or omissions which resulted
in such Losses as well as any other relevant equitable considerations. Benefits
received by the Company shall be deemed to be equal to the sum of (x) the total
net proceeds from the Initial Placement (before deducting expenses) as set forth
on the cover page of the Offering Memorandum and (y) the total amount of
Liquidated Damages that the Company was not required to pay as a result of
registering the Securities and Common Stock issued upon conversion thereof
covered by the Shelf Registration Statement which resulted in such Losses.
Benefits received by the Initial Purchasers shall be deemed to be equal to the
total purchase discounts and commissions as set forth on the cover page of the
Offering Memorandum, and benefits received by any other Holders shall be deemed
to be equal to the value of receiving Securities or the Common Stock issuable
upon conversion thereof registered under the Act. Benefits received by any
Underwriter shall be deemed to be equal to the total underwriting discounts and
commissions, as set forth on the cover page of the Prospectus forming a part of
the Shelf Registration Statement (or the applicable Prospectus supplement) which
resulted in such Losses. Relative fault shall be determined by reference to
whether any untrue statement or omission or alleged untrue statement or omission
relates to information provided by the indemnifying party, on the one hand, or
by the indemnified party, on the other hand. The parties agree that it would not
be just and equitable if contribution were determined by pro rata allocation or
any other method of allocation which does not take account of the equitable
considerations referred to above. Notwithstanding the provisions of this
paragraph (d), no person guilty of fraudulent misrepresentation (within the
meaning of Section 1 l(f) of the Act) shall be entitled to contribution from any
person
<PAGE>

who was not guilty of such fraudulent misrepresentation. For purposes of this
Section 5, each person who controls a Holder within the meaning of either the
Act or the Exchange Act and each director, officer, employee and agent of such
Holder shall have the same rights to contribution as such Holder, and each
person who controls the Company within the meaning of either the Act or the
Exchange Act, each officer of the Company who shall have signed the Shelf
Registration Statement and each director of the Company shall have the same
rights to contribution as the Company, and each person who controls an
Underwriter within the meaning of either the Act or the Exchange Act and each
officer and director of each Underwriter shall have the same rights to
contribution as such Underwriter, subject in each case to the applicable terms
and conditions of this paragraph (d).

(e) The provisions of this Section 5 will remain in full force and effect,
regardless of any investigation made by or on behalf of any Holder, any
Underwriter or the Company or any of the officers, directors or controlling
persons referred to in Section 5 hereof, and will survive the sale by a Holder
of Securities or shares of Common Stock covered by a Shelf Registration
Statement.

6. Miscellaneous.

(a) No Inconsistent Agreements. The Company has not, as of the date hereof,
entered into nor shall it, on or after the date hereof, enter into, any
agreement with respect to its securities that is inconsistent with the rights
granted to the Holders herein or otherwise conflicts with the provisions hereof.

(b) Amendments and Waivers. The provisions of this Agreement, including the
provisions of this sentence, may not be amended, qualified, modified or
supplemented, and waivers or consents to departures from the provisions hereof
may not be given, unless the Company has obtained the written consent of the
Majority Holders; provided that with respect to any matter that directly or
indirectly affects the rights of the Initial Purchasers hereunder, the Company
shall obtain the written consent of each of the Initial Purchasers against which
such amendment, qualification, supplement, waiver or consent is to be effective.
Notwithstanding the foregoing (except the foregoing proviso), a waiver or
consent to departure from the provisions hereof with respect to a matter that
relates exclusively to the rights of Holders whose Securities or Common Stock
are being sold pursuant to a Shelf Registration Statement and that does not
directly or indirectly affect the rights of other Holders may be given by the
Majority Holders, determined on the basis of Securities or Common Stock issued
upon conversion thereof being sold rather than registered under such Shelf
Registration Statement.

(c) Notices. All notices and other communications provided for or permitted
hereunder shall be made in writing by hand-delivery, first-class mail,
telecopier, or air courier guaranteeing overnight delivery:

            (1) if to you, initially at the address set forth in the Purchase
      Agreement;

            (2) if to any other Holder, at the most current address given by
      such Holder to the Company in accordance with the provisions of this
      Section 6(c), which address initially is, with respect to each Holder, the
      address of such Holder maintained by the Registrar under the Indenture or,
      in the case of Common Stock, the address maintained by the registrar of
      the Common Stock, with a copy in like manner to Salomon Smith Barney Inc.;
      and

            (3) if to the Company, initially at its address set forth in the
      Purchase Agreement.

      All such notices and communications shall be deemed to have been duly
given when received, if delivered by hand or air courier, and when sent, if sent
by first-class mail or telecopier.

      The Initial Purchasers or the Company by notice to the other may designate
additional or different addresses for subsequent notices or communications.

(d) Successors and Assigns. This Agreement shall inure
<PAGE>

to the benefit of and be binding upon the successors and assigns of each of the
parties, including, without the need for an express assignment or any consent by
the Company thereto, subsequent Holders. The Company hereby agrees to extend the
benefits of this Agreement to any Holder and Underwriter and any such Holder and
Underwriter may specifically enforce the provisions of this Agreement as if an
original party hereto. In the event that any other person shall succeed to the
Company under the Indenture as provided in Article VII thereof, then such
successor shall enter into an agreement, in form and substance reasonably
satisfactory to the Initial Purchasers, whereby such successor shall assume all
of the Company's obligations under this Agreement.

(e) Counterparts. This agreement may be executed in any number of counterparts
and by the parties hereto in separate counterparts, each of which when so
executed shall be deemed to be an original and all of which taken together shall
constitute one and the same agreement.

(f) Headings. The headings in this Agreement are for convenience of reference
only and shall not limit or otherwise affect the meaning hereof.

(g) GOVERNING LAW. THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK APPLICABLE TO AGREEMENTS MADE
AND TO BE PERFORMED IN SAID STATE, WITHOUT REGARD, TO THE EXTENT PERMITTED BY
APPLICABLE LAW, TO THE CONFLICTS OF LAW RULES THEREOF.

(h) Severability. In the event that any one of more of the provisions contained
herein, or the application thereof in any circumstances, is held invalid,
illegal or unenforceable in any respect for any reason, the validity, legality
and enforceability of any such provision in every other respect and of the
remaining provisions hereof shall not be in any way impaired or affected
thereby, it being intended that all of the rights and privileges of the parties
shall be enforceable to the fullest extent permitted by law.

(i) Securities Held by the Company, etc. Whenever the consent or approval of
Holders of a specified percentage of principal amount of Securities or the
Common Stock issuable upon conversion thereof is required hereunder, Securities
or the Common Stock issued upon conversion thereof held by the Company or its
Affiliates (other than subsequent Holders of Securities or the Common Stock
issued upon conversion thereof if such subsequent Holders are deemed to be
Affiliates solely by reason of their holdings of such Securities) shall not be
counted in determining whether such consent or approval was given by the Holders
of such required percentage.

      Please confirm that the foregoing correctly sets forth the agreement
between the Company and you.

              Very truly yours,

              DOUBLECLICK INC.


      _____________________________________
      Name:
      Title:

The foregoing Agreement is hereby
confirmed and accepted as of the date
first above written.

SALOMON SMITH BARNEY INC.
BT ALEX.BROWN INCORPORATED
DONALDSON, LUFKIN & JENRETTE SECURITIES CORPORATION

For themselves and the other Initial
Purchases named in Schedule I to the
Purchase Agreement

BY: SALOMON SMITH BARNEY INC.


By:
    Name:
    Title:
<PAGE>

                                    EXHIBIT A

                                DoubleClick Inc.

                        Notice of Registration Statement

                                       and

                      Selling Securityholder Questionnaire

      Reference is hereby made to the Registration Agreement (the "Registration
Agreement") between DoubleClick Inc., a Delaware corporation (the "Company"),
and the Initial Purchasers named therein. Pursuant to the Registration
Agreement, the Company has filed or will file with the United States Securities
and Exchange Commission (the "Commission") a registration statement on Form S-3
(the "Shelf Registration Statement") for the registration and resale under Rule
415 of the Securities Act of 1933, as amended (the "Securities Act"), of the
Company's 4.75% Convertible Subordinated Notes due 2006 (the "Securities"), and
the shares of the Company's common stock, par value $.001 per share (the "Common
Stock"), issuable upon conversion thereof. A copy of the Registration Agreement
is attached hereto. All capitalized terms not otherwise defined herein shall
have the meanings ascribed thereto in the Registration Agreement.

      Each holder and beneficial owner of Transfer Restricted Securities is
entitled to have its Transfer Restricted Securities included in the Shelf
Registration Statement. In order to have Transfer Restricted Securities included
in the Shelf Registration Statement, this Notice of Registration Statement and
Selling Securityholder Questionnaire ("Notice and Questionnaire") must be
completed, executed and delivered to the Company's counsel at the following
address, for receipt ON OR BEFORE [DEADLINE FOR RESPONSE]: [NAME AND ADDRESS OF
COUNSEL]. Holders or beneficial owners of Transfer Restricted Securities who do
not complete, execute and return this Notice and Questionnaire by such date (i)
will not be named as selling securityholders in the Shelf Registration Statement
and (ii) may not use the Prospectus forming a part thereof for resales of
Transfer Restricted Securities, subject, however, to the Company's obligations
under Section 2(b)(2) of the Registration Agreement.

      Certain legal consequences arise from being named as a selling
securityholder in the Shelf Registration Statement and related Prospectus.
Accordingly, holders and beneficial owners of Transfer Restricted Securities are
advised to consult their own securities law counsel regarding the consequences
of being named or not being named as a selling securityholder in the Shelf
Registration Statement and related Prospectus.

                                    ELECTION

      The undersigned (the "Selling Securityholder") hereby elects to include in
the Shelf Registration Statement the Transfer Restricted Securities held or
beneficially owned by it and listed below in Item (3)(b). The undersigned, by
signing and returning this Notice and Questionnaire, agrees to be bound with
respect to such Transfer Restricted Securities by the terms and conditions of
this Notice and Questionnaire and the Registration Agreement, including, without
limitation, the indemnification set forth in Section 5 of the Registration
Agreement, as if the undersigned Selling Securityholder were an original party
thereto.
<PAGE>

QUESTIONNAIRE

(1) (a) Full legal name of Selling Securityholder:

      (b) Full legal name of registered holder (if not the same as in (a) above)
of Transfer Restricted Securities listed in (3) below (if the Transfer
Restricted Securities are held through a broker-dealer or other third party and,
as a result, you do not know the legal name of the registered holder, please
complete Item (l)(c) below):

      (c) Full legal name of broker-dealer or other third party through which
Transfer Restricted Securities listed in (3) below are held:

(2) Address for notices to Selling Securityholder:

Telephone:
Fax:
Contact Person:

(3) Beneficial ownership of Transfer Restricted Securities.

      Except as set forth below in this Item (3), the undersigned does not
beneficially own any Securities or shares of Common Stock which constitute
Transfer Restricted Securities.

      (a) Principal amount of Securities constituting Transfer Restricted
Securities beneficially owned:

      Number of shares of Common Stock, if any, constituting Transfer Restricted
Securities (include only shares of Common Stock which have actually been issued,
not shares issuable upon future conversion of Securities):

      The undersigned also may be deemed to beneficially own such number of
shares of Common Stock as may be issued from time to time upon conversion of the
Securities listed in Item (3)(a) above.

      (b) Principal amount of Securities and number of shares of outstanding
Common Stock constituting Transfer Restricted Securities which the undersigned
wishes to be included in the Shelf Registration Statement:

      Unless otherwise indicated in the space provided below, all Securities,
all shares of Common Stock listed in response to Item (3)(a) above, and all
shares of Common Stock issuable upon conversion of the Securities listed in
response to Item (3)(b)above, will be included in the Shelf Registration
Statement. If the undersigned does not wish all such Securities or shares of
Common Stock to be so included, please indicate below the number of such shares
to be included:

(4) Beneficial ownership of other securities of the Company:

      Except as set forth below in this item (4), the undersigned Selling
Securityholder is not the beneficial or registered owner of any shares of Common
Stock or any other securities of the Company, other than Securities and shares
of Common Stock listed above in Item (3).

      State any exceptions here:
<PAGE>

(5) Relationships with the Company:

      Except as set forth below, neither the Selling Securityholder nor any of
its officers, directors or 5% or greater stockholders has held any position or
office or has had any other material relationship with the Company (or its
predecessors or affiliates)during the past three years.

      State any exceptions here:

(6) Plan of Distribution:

      Except as set forth below, the undersigned Selling Securityholder intends
to distribute the Transfer Restricted Securities listed above in Item (3) only
as follows (if at all): Such Transfer Restricted Securities may be sold from
time to time by the undersigned Selling Securityholder (i) to or through
underwriters, brokers or dealers; (ii) directly to one or more other purchasers;
(iii) through agents on a best-efforts basis or otherwise; or (iv) through a
combination of any such methods of sale. Such Transfer Restricted Securities may
be sold from time to time in one or more transactions at a fixed price or
prices, which may be changed, at market prices prevailing at the time of sale,
at prices related to such prevailing market prices, at varying prices determined
at the time of sale, or at negotiated prices. Such sales may be effected in
transactions (which may involve crosses or block transactions) (i) on any
national securities exchange or quotation service on which the Transfer
Restricted Securities may be listed or quoted at the time of sale, (ii) in the
over-the-counter market, (iii) in transactions otherwise than on such exchanges
or services or in the over-the-counter market, or (iv) through the writing of
options. In connection with sales of the Transfer Restricted Securities or
otherwise, the Selling Securityholder may enter into hedging transactions with
brokers-dealers or others, which may in turn engage in short sales of the
Transfer Restricted Securities in the course of hedging the positions they
assume. The Selling Securityholder may also sell Transfer Restricted Securities
short and deliver Transfer Restricted Securities to close out such short
positions, or loan or pledge Transfer Restricted Securities to brokers-dealers
or others that in turn may sell such securities. The Selling Securityholder may
pledge or grant a security interest in some or all of the Transfer Restricted
Securities owned by it and, if it defaults in the performance of its secured
obligations, the pledgees or secured parties may offer and sell the Transfer
Restricted Securities from time to time pursuant to the Prospectus. The Selling
Securityholder also may transfer and donate shares in other circumstances in
which case the transferees, donees, pledgees or other successors in interest
will be the selling stockholders for purposes of the Prospectus. The Selling
Securityholder may sell short the Common Stock and may deliver the Prospectus in
connection with such short sales and use the shares covered by the Prospectus to
cover such short sales.

      State any exceptions here:

      By signing below, the Selling Securityholder acknowledges that it
understands its obligation to comply, and agrees that it will comply, with the
provisions of the Securities Exchange Act of 1934, as amended, and the rules and
regulations thereunder, particularly Regulation M and the prospectus delivery
requirements under the Securities Act.

      In the event that the Selling Securityholder transfers all or any portion
of the Transfer Restricted Securities listed in Item (3) above after the date on
which such information is provided to the Company (other than a transaction as a
result of which such securities shall no longer be Transfer Restricted
Securities), the Selling Securityholder agrees to notify the transferees at the
time of the transfer of its rights and obligations under this Notice and
Questionnaire and the Registration Agreement.

      By signing below, the Selling Securityholder consents to the disclosure of
the information contained herein in its answers to Items (1) through (6) above
and the inclusion of such information in the Shelf Registration Statement and
related Prospectus. The Selling Securityholder understands that such information
will be relied upon by the Company in connection with the preparation of the
Shelf Registration Statement and related Prospectus.
<PAGE>

      The Selling Securityholder agrees to promptly notify the Company of any
inaccuracies or changes in the information provided herein which may occur
subsequent to the date hereof at any time while the Shelf Registration Statement
remains in effect. All notices hereunder and pursuant to the Registration
Agreement shall be made in writing, by hand-delivery, first class mail, or air
courier guaranteeing overnight delivery as follows:

            DoubleClick Inc.
            41 Madison Avenue, 32nd Floor
            New York, New York 10010
            Attention: Chief Financial Officer

      Once this Notice and Questionnaire is executed by the Selling
Securityholder and received by the Company, the terms of this Notice and
Questionnaire, and the representations and warranties contained herein, shall be
binding on, shall inure to the benefit of and shall be enforceable by the
respective successors, heirs, personal representatives, and assigns of the
Company and the Selling Securityholder (with respect to the Transfer Restricted
Securities beneficially owned by such Selling Securityholder and listed in Item
(3)(b) above). This Agreement shall be governed by and construed in accordance
with the internal laws of the State of New York.

      IN WITNESS WHEREOF, the undersigned, by authority duly given, has caused
this Notice and Questionnaire to be executed and delivered either in person or
by its duly authorized agent.

Dated:

                              Selling Securityholder
                    (Print/type full legal name of beneficial
                    owner of Transfer Restricted Securities).


                    By:
                    Name:
                    Title:
<PAGE>

                                    EXHIBIT B

                   FORM OF LETTER TO BE PROVIDED BY ISSUER TO

                          THE DEPOSITORY TRUST COMPANY

The Depository Trust Company
7 Hanover Square, 23rd Floor
New York, NY 10004

      Re.   4.75% Convertible Subordinated Notes due 2006 (the "Securities") of
            DoubleClick Inc.

Ladies and Gentlemen:

      Please be advised that the Securities and Exchange Commission has declared
effective a Registration Statement on Form S-3 under the Securities Act of 1933,
as amended, with regard to all of the Securities referenced above. Accordingly,
there is no longer any restriction as to whom such Securities may be sold and
any restrictions on the CUSIP designation are no longer appropriate and may be
removed. I understand that upon receipt of this letter, DTC will remove any stop
or restriction on its system with respect to this issue.

      As always, please do not hesitate to call if we can of further assistance.

                                  Very truly yours,


                                  By:
                                  Authorized Officer