Document:

EXHIBIT 10.1

                                                                  Execution copy

                             ALLION HEALTHCARE, INC.

                         SUBORDINATED SECURITY AGREEMENT

                  THIS SUBORDINATED SECURITY AGREEMENT, dated as of May 1, 2003
(this "SECURITY Agreement"), by and among ALLION HEALTHCARE, INC., a Delaware,
corporation ("BORROWER"), those individuals identified on the signature pages
hereto as Lenders (each individually, a "Lender", and together, "Lenders") and
Darin A. Peterson, or any successor thereof, as collateral agent for the Lenders
(in such capacity, "COLLATERAL AGENT").

                             PRELIMINARY STATEMENTS

                  1. Pursuant to that certain Stock Purchase Agreement, of even
date herewith, by and among Borrower and the Lenders, parties thereto (as
modified and amended from time to time, the "PURCHASE AGREEMENT"), Borrower
executed four (4) promissory notes (each, a "NOTE" and collectively, the
"NOTES") in the aggregate principal amount of $2,400,000 (collectively, the
"LOANS") payable to the Lenders and in connection therewith, Borrower hereby
grants to Collateral Agent, as agent for the Lenders and for the ratable benefit
of the Lenders, a security interest in the Collateral (as defined below) as
further set forth herein. Capitalized terms used but not otherwise defined
herein shall have the meanings ascribed to them in the Purchase Agreement.

                  2. Pursuant to the Purchase Agreement, it is a condition
precedent to the obligation of each of the Lenders to consummate the
transactions contemplated by the Purchase Agreement that Borrower shall have
granted a security interest in the Collateral as contemplated by this Security
Agreement to secure the payment obligations of Borrower.

                  NOW, THEREFORE, Borrower, Collateral Agent and each of the
Lenders hereby agrees as follows:

                  SECTION 1. GRANT OF SECURITY. As security for the prompt and
complete payment and performance when due of the Secured Obligations, Borrower
hereby grants to the Collateral Agent, as agent for the Lenders and for the
benefit of each of the Lenders, a security interest in and lien on all of
Borrower's right, title and interest in and to all of Borrower's assets to the
extent that such assets are existing and owned by Borrower as of the date hereof
and all substitutions, replacements and proceeds of such assets, including but
not limited to all of the following, to the extent so owned and existing as of
the date hereof and all substitutions, replacements and proceeds of such assets
(the "COLLATERAL"):

                  (a) All machinery, furnishings, fixtures, service vehicles,
supplies and other equipment, together with all attachments, components, parts
and accessories installed thereon or affixed thereto (the "EQUIPMENT");

                  (b) All goods held for sale or lease or to be furnished under
contracts of service, wherever located, together with all goods and materials
used or usable in manufacturing, processing, packaging or shipping same; in all
stages of production, from raw materials through work-in-process to finished
goods (the "INVENTORY");

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                  (c) All other goods of any nature whatsoever;

                  (d) All (i) (A) rights to payment for goods sold or services
rendered by Borrower, including all accounts arising from sales or rendition of
services made under any of Borrower's trade names or styles or through any of
Borrower's divisions, regardless of how such right is evidenced, whether secured
or unsecured (and whether or not specifically listed on schedules furnished to
the Lenders) (the "ACCOUNTS RECEIVABLE"), and (B) other accounts; (ii) unpaid
seller's rights (including rights of rescission, replevin, reclamation and
stoppage in transit) relating to the foregoing or arising therefrom; (iii)
rights to any goods represented by any of the foregoing, including rights to
returned or repossessed goods; (iv) reserves and credit balances arising under
any of the foregoing; (v) guarantees, letters of credit, collateral or other
supporting obligations supporting or securing any of the foregoing; and (vi)
insurance policies or rights relating to any of the foregoing;

                  (e) All (i) instruments, (ii) documents, (iii) contract
rights, (iv) chattel paper, (v) letters of credit, (vi) letter-of-credit rights,
(vii) claims and causes of action against any other Person, however arising, and
(viii) general intangibles, whether or not for the payment of money, including,
but not limited to, all (A) rights to tax refunds or other payments of every
kind or nature, including rights to the payment of letters of credit; (B)
copyrights, rights in or licenses of copyrights and marks subject to copyright
protection, in whole or in part, and all renewals or extensions of any of the
foregoing (the "COPYRIGHTS"); (C) trade names, trademarks, service marks, trade
styles, designs, logos, indicia, corporate names, company names and fictitious
business names, in each case, together with all associated goodwill including,
without limitation, the trademark applications set forth on SCHEDULE II hereto
(the "Trademarks"); (D) (i) patents now existing, all registrations and
recordings thereof, and all applications in connection therewith, including,
without limitation, registrations, recordings and applications in the United
States Patent and Trademark Office or in any similar office or agency of the
United States, any State thereof or any other country or any political
subdivision thereof, including, without limitation, those listed on SCHEDULE II
hereto together with all the rights, benefits and privileges derived therefrom,
and (ii) all design and utility patents, utility models and registered designs
(including all reissues, divisions, continuations, continuations-in-part,
reexaminations and extensions thereof) (collectively, the "PATENTS"); (E)
computer programs and all intellectual property rights therein (other than such
programs and rights in which, by their terms enforceable under applicable law,
no security interest may be granted); and (F) other proprietary information;

                  (f) All investment property, including, without limitation,
all securities and capital stock or other interests in any other Person whether
certificated or uncertificated; all warrants, options and other rights to
acquire securities, capital stock or other interests in any other Person; all
securities entitlements; and all securities accounts, together with all
financial assets credited thereto;

                  (g) All cash and cash equivalents, including, without
limitation, money, demand deposit accounts and other deposit accounts;

                                      -2-
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                  (h) All governmental approvals, licenses, franchises and
authorizations, to the maximum extent permitted by applicable law;

                  (i) All property and interests in property of Borrower
currently in the actual possession, custody or control of the Lenders in any way
and for any purpose (whether for safekeeping, deposit, custody, pledge,
transmission, collection or otherwise);

                  (j) All books and records;

                  (k) All other property and interests in property of Borrower
constituting personal property; and

                  (l) All of the assets of Borrower listed on SCHEDULES I, II
and III attached hereto.

                  SECTION 2. SECURITY FOR OBLIGATIONS.

                  (a) This Security Agreement and the Collateral secure (i) the
prompt and complete payment when due of the outstanding principal and interest
of Borrower pursuant to the Notes held by the Lenders and (ii) all obligations
of Borrower to the Collateral Agent hereunder (collectively, the "SECURED
OBLIGATIONS").

                  (b) Notwithstanding the foregoing, Borrower agrees to use
reasonable efforts to obtain, within four (4) months of the date hereof, a
letter of credit from a commercial bank as security for Borrower's payment
obligations under the Notes. In the event that such letter of credit is obtained
on terms reasonably acceptable to the Lenders, the Lenders acknowledge and agree
that immediately upon delivery of such letter of credit to the Collateral Agent,
(i) the letter of credit will replace this Security Agreement, in whole, as
security for the Secured Obligations, (ii) the letter of credit will be deemed
to be the sole security of the Lenders with respect to Borrower's payment
obligations under the Notes, and (iii) this Security Agreement will become null
and void and of no further force and effect (the procurement of such letter of
credit being referred to herein as the "L/C SUBSTITUTION").

                  SECTION 3. BORROWER REMAINS LIABLE. Anything herein to the
contrary notwithstanding, (a) Borrower shall remain liable under the contracts
and agreements included in the Collateral to the extent set forth therein to
perform all of its duties and obligations thereunder to the same extent as if
this Security Agreement had not been executed, (b) the exercise by the
Collateral Agent of any rights hereunder shall not release Borrower from any of
its duties or obligations under the contracts and agreements included in the
Collateral, and (c) the Collateral Agent shall not have any obligation or
liability under the contracts and agreements included in the Collateral by
reason of this Security Agreement, nor shall the Collateral Agent be obligated
to perform any of the obligations or duties of Borrower thereunder or to take
any action to collect or enforce any claim for payment assigned hereunder.

                  SECTION 4. REPRESENTATIONS AND WARRANTIES. Borrower represents
and warrants to the Collateral Agent, as follows:

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                  (a) Borrower is a corporation duly incorporated, validly
existing and in good standing under the laws of the State of Delaware and is
qualified to do business and in good standing in all other states and
jurisdictions in which the failure to be so qualified and in good standing would
have a material adverse effect on the assets, properties or condition (financial
or otherwise) of Borrower or a material adverse effect on the ability of
Borrower to enforce the collection of Accounts Receivable due from customers
residing in such locations.

                  (b) Borrower's execution, delivery and performance of this
Security Agreement and the Notes does not violate any provision of Borrower's
Certificate of Incorporation or Bylaws, each as may be amended as of the date
hereof.

                  (c) Borrower has the requisite power and authority to enter
into this Security Agreement and the Notes and perform its obligations under the
terms of this Security Agreement and the Notes. All corporate action on the part
of Borrower, its officers and directors necessary for the authorization,
execution and delivery of this Security Agreement and the Notes has been taken.
This Security Agreement and the Notes have been duly authorized by Borrower and,
upon due execution and delivery by Borrower of this Security Agreement and the
Notes, this Security Agreement and the Notes will each be a valid and binding
agreement of Borrower, enforceable in accordance with its respective terms,
except as enforceability may be limited by bankruptcy, insolvency,
reorganization, moratorium or similar laws affecting creditors' rights generally
or by equitable principles.

                  (d) All of the Equipment and Inventory (i) were acquired in
the ordinary course of business and (ii) are located at the places specified on
SCHEDULE I hereto. The principal place of business and chief executive office of
Borrower and the office where Borrower keeps its records concerning Accounts
Receivable and other Collateral are located at the address specified in SCHEDULE
I hereto.

                  (e) Except for Permitted Liens (as defined below), Borrower
owns the Collateral free and clear of any Lien (as defined below). For purposes
of this Agreement, "LIEN" means any mortgage, deed of trust, pledge, security
interest, hypothecation, assignment, deposit arrangement, encumbrance, lien
(statutory or other), preference or other security agreement or preferential
arrangement, charge or encumbrance of any kind or nature whatsoever (including,
without limitation, any conditional sale or other title retention agreement, any
financing lease having substantially the same economic effect as any of the
foregoing, and the filing of any financing statement under the Uniform
Commercial Code of the State of Delaware (the "UCC") or comparable law of any
jurisdiction to evidence any of the foregoing). For purpose of this Agreement,
"PERMITTED LIEN" means (i) the Lien created hereunder in favor of Collateral
Agent on behalf and for the benefit of Lenders; (ii) any Liens existing on the
date of this Agreement and set forth on SCHEDULE I hereto; (iii) Liens for
taxes, fees, assessments or other governmental charges or levies, either not
delinquent or being contested in good faith by appropriate proceedings, provided
the same have no priority over the Collateral Agent's security interests; (iv)
Liens (1) upon or in any Equipment acquired or held by Borrower to secure the
purchase price of such Equipment or indebtedness incurred solely for the purpose
of financing the acquisition of such Equipment or (2) existing on such Equipment
at the time of its acquisition, provided that the Lien is confined solely to the
Equipment so acquired, improvements thereon and the proceeds of such Equipment;
(v) leases or subleases and licenses or sublicenses granted to others in the

                                      -4-

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ordinary course of Borrower's business if such are otherwise permitted under
this Security Agreement and do not interfere in any material respect with the
business of Borrower; (vi) any right, title or interest of a licensor under a
license provided that such license or sublicense does not prohibit the grant of
the security interest granted hereunder; (vii) Liens in favor of customs and
revenue authorities arising as a matter of law to secure payment of customs
duties in connection with the importation of goods; (viii) Liens arising solely
by virtue of any statutory or common law provision relating to banker's liens,
rights of setoff or similar rights and remedies as to deposit accounts or other
funds maintained with a creditor depository institution; (ix) Liens securing
capital lease obligations on assets subject to such capital leases and Liens on
equipment leased by Borrower pursuant to an operating lease in the ordinary
course of Borrower's business (including proceeds thereof and accessions
thereto), all incurred solely for the purpose of financing the lease of such
equipment (including Liens arising from UCC financing statements regarding such
leases); and (x) Liens incurred in connection with the extension, renewal or
refinancing of the indebtedness secured by Liens of the type described in
clauses (ii) and (iv) above, provided that any extension, renewal or replacement
Lien shall be limited to the property encumbered by the existing Lien and the
principal amount of the indebtedness being extended, renewed or refinanced does
not increase.

                  (f) Borrower has exclusive possession and control of the
Equipment and Inventory.

                  (g) SCHEDULE II hereto sets forth a complete and correct list
of all Patents, Trademarks and Copyrights owned or applied for (and pending) by
Borrower as of the date hereof. Borrower has the right to use all Patents,
Trademarks and Copyrights and all computer programs and other rights, free from
materially burdensome restrictions, which are necessary for the operation of its
business as presently conducted. To the knowledge of Borrower, there is no
pending or threatened claim or litigation against or related to the validity of
any of the Patents, Trademarks or Copyrights or any computer program or other
right of Borrower.

                  (h) Except for Permitted Liens, this Security Agreement
creates a valid first priority Lien in the Collateral, securing the payment of
the Secured Obligations. All actions legally necessary to perfect and protect
such security interest have been duly taken.

                  (i) No authorization, approval or other action by, and no
notice to or filing with, any governmental or regulatory agency or authority is
required either (1) for the grant by Borrower of the security interest granted
hereby or for the execution, delivery or performance of this Security Agreement
by Borrower or (2) other than (i) the filing of a financing statement on Form
UCC-1 with the Secretary of State of the State of Delaware or (ii) filings with
the United States Patent and Trademark Office in connection with the assignments
of the Copyrights, Trademarks and Patents, for the perfection of such security
interest or the exercise by the Collateral Agent of its rights and remedies
hereunder.

                  (j) Except as set forth on SCHEDULE I hereto, there are no
actions or proceedings pending by or against Borrower before any court or
administrative agency which could have a material adverse effect on Borrower's
business or a material adverse effect on Collateral Agent's security interest in
the Collateral.

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<PAGE>

                  (k) No default, and no event which with the passage of time,
or the giving of notice, or both, would be reasonably likely to give rise to a
default, shall exist under the provisions of any instrument or agreement
evidencing, governing or otherwise relating to any indebtedness of Borrower, or
with respect to any other agreement, a default under which could have a material
adverse effect upon Borrower's ability to perform its obligations under this
Security Agreement, the Notes, and any other agreement or instrument executed
pursuant to or in connection with the Secured Obligations (collectively, the
"LOAN DOCUMENTS"), or the validity or enforceability of, or Lenders' rights and
remedies under, any of the Loan Documents.

                  (l) All existing commercial tort claims owned by Borrower are
set forth and described on SCHEDULE III hereto.

                  SECTION 5. FURTHER ASSURANCES.

                  (a) Borrower agrees that from time to time, at the expense of
Borrower, Borrower will promptly execute or otherwise authenticate and deliver
all further instruments, documents and other records and take all further
action, that may be reasonably necessary or desirable, or that the Collateral
Agent may request, in order to perfect and protect any security interest granted
or purported to be granted hereby or to enable the Collateral Agent to exercise
and enforce its rights and remedies hereunder with respect to any Collateral.
Without limiting the generality of the foregoing, if any Account Receivable
shall be evidenced by a promissory note or other instrument or chattel paper,
Borrower will (1) deliver such to Collateral Agent duly endorsed and accompanied
by duly executed instruments of transfer or assignment and (2) authenticate (if
necessary) and file such financing or continuation statements, or amendments
thereto, and such other instruments, notices or other records, as may be legally
necessary, or as the Collateral Agent may request, in order to perfect and
preserve the security interest granted or purported to be granted hereby.

                  (b) Borrower hereby authorizes the Collateral Agent to file
one or more financing or continuation statements, and amendments thereto,
relative to all or any part of the Collateral without the signature of Borrower
where permitted by law. A carbon, photographic or other reproduction of this
Security Agreement or any financing statement covering the Collateral or any
part thereof shall be sufficient as a financing statement where permitted by
law.

                  (c) Borrower will furnish to the Collateral Agent, from time
to time, statements and schedules further identifying and describing the
Collateral and such other reports in connection with the Collateral as the
Collateral Agent may reasonably request, all in reasonable detail. Without
limiting the generality of the foregoing: (i) Borrower shall, from time to time
and upon request of the Collateral Agent, execute and deliver to the Collateral
Agent, such confirmatory schedules of Accounts Receivable, and such other
appropriate reports designating, identifying and describing the Accounts
Receivable, as the Collateral Agent may reasonably request; and (ii) if any
commercial tort claim should hereafter arise ("ADDITIONAL TORT CLAIM"), Borrower
shall promptly advise the Collateral Agent in writing, supplementing SCHEDULE
III hereto, which supplement shall constitute a grant by Borrower to the
Collateral Agent of a security interest therein, on the terms, and subject to
the conditions, set forth in the Security Agreement, and Borrower's
authorization to file, or to amend, such financing statements as the Collateral
Agent may deem necessary or advisable to perfect its security interest in such
Additional Tort Claim. In addition, upon the Collateral Agent's request,
Borrower shall provide the Collateral Agent with copies of agreements with, or
purchase orders from, Borrower's customers, of invoices to customers and proof
of shipment or delivery and such other documentation and information relating to
the Accounts Receivable and other Collateral as the Collateral Agent may from

                                      -6-

<PAGE>

time to time reasonably request to the extent Borrower maintains such
documentation in the ordinary course of its business. Failure to provide the
Collateral Agent with any of the foregoing shall in no way affect, diminish,
modify or otherwise limit the Lien granted herein. Borrower hereby authorizes
the Collateral Agent to regard its printed name or rubber stamp signature on
assignment schedules or invoices as the equivalent of a manual signature by an
authorized officer or agent of Borrower.

                  (d) Subject to the priority of the Senior Indebtedness (as
defined in the Notes), Borrower will defend the Collateral against all claims
and demands of all persons (other than the Collateral Agent) claiming an
interest therein. Borrower will pay promptly when due all property and other
taxes, assessments and governmental charges or levies imposed upon, and all
claims (including claims for labor, materials and supplies) against, the
Collateral, except to the extent where there is a good faith contest to the
validity thereof and is reserved against (to the extent required by GAAP) by
Borrower. In connection with any such good faith contest Borrower will, at the
request of the Collateral Agent, promptly provide a bond, cash deposit or other
security reasonably satisfactory to protect the security interest of the
Collateral Agent should such good faith contest be unsuccessful.

                  SECTION 6. EQUIPMENT, INVENTORY AND TRADEMARKS. Borrower
shall:

                  (a) Keep the Equipment and Inventory (other than Inventory
sold in the ordinary course of business) at the places therefor specified on
SCHEDULE I hereto or, upon thirty (30) calendar days prior written notice to the
Collateral Agent, at such other places in jurisdictions where all action
required by Section 5 hereof shall have been taken with respect to the Equipment
and Inventory;

                  (b) Cause the Equipment necessary for the conduct of its
business to be maintained and preserved in the same condition, repair and
working order as when new, ordinary wear and tear excepted, and shall forthwith,
or in the case of any loss or damage to any of the Equipment as quickly as
practicable after the occurrence thereof, make or cause to be made all repairs,
replacements, and other improvements in connection therewith which are necessary
or desirable to such end;

                  (c) Permit the Collateral Agent or any agent thereof to have
access to the Inventory and Equipment for purposes of inspection during normal
business hours and upon reasonable notice to Borrower;

                  (d) Promptly notify the Collateral Agent in writing of any
material loss or damage to the Inventory or Equipment;

                  (e) Not sell, assign, lease, mortgage, transfer or otherwise
dispose of any interest in the Inventory or Equipment, except as otherwise
permitted under Section 9(a) hereof;

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<PAGE>

                  (f) Not use or permit the Inventory or Equipment to be used
for any unlawful purpose or in violation of any law or for hire;

                  (g) Except for collateral securing a purchase-money obligation
incurred in compliance with ss.9-103 of the UCC, not permit the Equipment to
become a part of or to be affixed to any real property of any person; and

                  (h) Take all reasonable steps to maintain and enforce the
Trademarks, Patents and Copyrights material to the conduct of its business,
including but not limited to (1) paying of all fees, (2) prosecuting infringers
if failure to do so would materially and adversely affect the business of
Borrower and (3) diligently pursuing any application or registration material to
the business of Borrower.

                  SECTION 7.    INSURANCE.
                                ---------

                  (a) Borrower shall, at its own expense, maintain insurance
with respect to the Equipment and Inventory in such amounts, against such risks,
in such form and with such insurers, as Borrower shall deem reasonable and
necessary from time to time. Each policy for: (x) liability insurance shall
provide for all losses to be paid on behalf of the holder of the Senior
Indebtedness (the "SENIOR LENDER"), the Collateral Agent and Borrower as their
respective interests may appear; and (y) property damage insurance shall provide
for all losses to be paid directly to the Senior Lender, the Collateral Agent
and Borrower, as appropriate. Each such policy shall in addition: (1) name the
Collateral Agent as insured party thereunder (without any representation or
warranty by or obligation upon the Collateral Agent) as its interests may
appear; (2) contain the agreement by the insurer that any loss thereunder shall
be payable to the Senior Lender and Collateral Agent notwithstanding any action,
inaction or breach of representation and warranty by Borrower; (3) provide that
there shall be no recourse against the Collateral Agent or any Lender for
payment of premiums or other amounts with respect thereto; and (4) provide that
at least thirty (30) calendar days prior written notice of amendment to,
cancellation of or lapse shall be given to the Collateral Agent by the insurer.
Borrower shall, if so requested by the Collateral Agent, deliver to the
Collateral Agent original or duplicate policies of such insurance and, as often
as the Collateral Agent may reasonably request, a report of an insurance broker
with respect to such insurance. Further, Borrower shall, at the request of the
Collateral Agent, duly execute and deliver instruments of assignment of such
insurance policies to comply with the requirements of Section 5 hereof and cause
the respective insurers to acknowledge notice of such assignment.

                  (b) Reimbursement under any liability insurance maintained by
Borrower pursuant to this Section 7 may be paid directly to the person who shall
have incurred liability covered by such insurance. In case of any loss involving
damage to Equipment or Inventory when subsection (c) of this Section 7 is not
applicable, Borrower shall make or cause to be made the necessary repairs to or
replacements of such Equipment or Inventory, and any proceeds of insurance
maintained by Borrower pursuant to this Section 7 shall be paid to Borrower as
reimbursement for the costs of such repairs or replacements.

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<PAGE>

                  (c) Upon the occurrence of any Default (as defined in the
Notes) all insurance payments in respect of such Equipment or Inventory shall be
paid to the Collateral Agent and applied to payment of the amounts due under the
Notes.

                   SECTION 8.   ACCOUNTS RECEIVABLE.
                                -------------------

                  (a) Borrower shall keep its principal place of business and
chief executive office and the office where it keeps its records concerning the
Accounts Receivable, at the location therefor specified on SCHEDULE I hereto or,
upon thirty (30) calendar days prior written notice to the Collateral Agent, at
such other locations in a jurisdiction where all action required by Section 5
hereof shall have been taken with respect to Accounts Receivable. Borrower will
hold and preserve such records and will permit representatives of the Collateral
Agent to inspect and make abstracts from such records. Borrower will not change
its name or jurisdiction of incorporation, its tax identification number or its
corporate structure, or merge with or into any other Person, or become
domesticated under the laws of any other jurisdiction without giving prior
notice to the Collateral Agent.

                  (b) Except as otherwise provided in this subsection (b),
Borrower shall continue to collect, at its own expense, all amounts due or to
become due to Borrower under the Accounts Receivable. In connection with such
collections, Borrower may take (and, at the Collateral Agent's discretion, shall
take) such action as Borrower or the Collateral Agent may deem necessary or
advisable to enforce collection of the Accounts Receivable; provided, however,
that the -13- have the right at any time, upon the occurrence
and during the continuance of a Default to notify the account debtors or
obligors under any Accounts Receivable of the assignment of such Accounts
Receivable to the Collateral Agent and to direct such account debtors or
obligors to make payment of all amounts due or to become due to Borrower
thereunder directly to the Collateral Agent and, upon such notification and at
the expense of Borrower, to enforce collection of any such Accounts Receivable,
and to adjust, settle or compromise the amount or payment thereof, in the same
manner and to the same extent as Borrower might have done. After receipt by
Borrower of the notice from the Collateral Agent referred to in the proviso to
the preceding sentence and as long as there is a Default, (1) all amounts and
proceeds (including instruments) received by Borrower in respect of the Accounts
Receivable shall be received in trust for the benefit of the Collateral Agent
hereunder, shall be segregated from other funds of Borrower and shall be
forthwith paid over to the Collateral Agent in the same form as so received
(with any necessary endorsement) to be held as cash collateral, or be applied as
provided by Section 12 hereof, as determined by the Collateral Agent, and (2)
Borrower shall not adjust, settle or compromise the amount or payment of any
Accounts Receivable, or release wholly or partly any account debtor or obligor
thereof, or allow any credit or discount thereon, other than any discount
allowed for prompt payment.

SECTION 9.        TRANSFER AND OTHER LIENS.  Borrower shall not:
                  ------------------------

                  (a) Sell, assign (by operation of law or otherwise) or
otherwise dispose of any of the Collateral, other than in connection with the
(i) sale of inventory and (ii) disposal of worn-out or obsolete equipment, all
in the ordinary course of business.

                                      -9-

<PAGE>

                  (b) Except for Permitted Liens, create or suffer to exist any
Lien upon or with respect to any of the Collateral to secure debt of any person.

                  SECTION 10. NOTES EQUALLY AND RATABLY SECURED; SUBORDINATION.
------------------------------------------------ (a) The Notes shall be equally
and ratably secured pursuant to the terms of this Security Agreement. Subject to
the rights of the Senior Lender, Borrower shall not make any offer to purchase
or otherwise pay either Lender without making the same offer to the other
Lender.

                  (b) Notwithstanding any other provision of this Security
Agreement to the contrary, all rights of the Collateral Agent under this
Security Agreement are subject to the subordination provisions contained in
Section 6 of the Notes.

                  SECTION 11. COLLATERAL AGENT. Darin A. Peterson is hereby
appointed Collateral Agent hereunder. Each Lender hereby authorizes Collateral
Agent to act as its agent in accordance with the terms of this Security
Agreement and the Notes. Collateral Agent agrees to act upon the express
conditions contained in this Security Agreement and the Notes, as applicable.
The provisions of this Section 11 are solely for the benefit of Collateral Agent
and Lenders and Borrower shall not have any rights as a third party beneficiary
of any of the provisions thereof. In performing its functions and duties under
this Security Agreement, Collateral Agent shall act solely as an agent of
Lenders and does not assume and shall not be deemed to have assumed any
obligation towards or relationship of agency or trust with or for Borrower.

                  (a) POWERS; DUTIES SPECIFIED. Each Lender irrevocably
authorizes Collateral Agent to take such action on such Lender's behalf and to
exercise such powers, rights and remedies hereunder and under the Notes as are
specifically delegated or granted to Collateral Agent by the terms hereof and
thereof, together with such powers, rights and remedies as are reasonably
incidental thereto. Collateral Agent shall have only those duties and
responsibilities that are expressly specified in this Security Agreement and the
Notes. Collateral Agent may exercise such powers, rights and remedies and
perform such duties by or through his agents or employees. Collateral Agent
shall not have, by reason of this Security Agreement or the Notes, a fiduciary
relationship in respect of any Lender or Borrower; nothing in this Security
Agreement or the Notes, expressed or implied, is intended to or shall be so
construed as to impose upon Collateral Agent any obligations in respect of this
Security Agreement or the Notes except as expressly set forth herein or therein.

                  (b) NO RESPONSIBILITY FOR CERTAIN MATTERS. Collateral Agent
shall not be responsible to any Lender for the execution, effectiveness,
genuineness, validity, enforceability, collectibility or sufficiency of this
Security Agreement or for any representations, warranties, recitals or
statements made herein or therein or made in any written or oral statements or
in any financial or other statements, instruments, reports or certificates or
any other documents furnished or made by Collateral Agent to Lenders or by or on
behalf of Borrower to Collateral Agent or any Lender in connection with this
Security Agreement or the Notes and the transactions contemplated thereby or for
the financial condition or business affairs of Borrower or any other Person
liable for the payment of any Secured Obligations, nor shall Collateral Agent be
required to ascertain or inquire as to the performance or observance of any of
the terms, conditions, provisions, covenants or agreements contained in any of
this Security Agreement or the Notes or as to the existence or possible
existence of any Default or potential Default.

                                      -10-

<PAGE>

                  (c) EXCULPATORY PROVISIONS. Neither Collateral Agent nor any
of his employees or agents shall be liable to Lenders for any action taken or
omitted by Collateral Agent under or in connection with any of this Security
Agreement or the Notes except to the extent caused by Collateral Agent's gross
negligence or willful misconduct. Collateral Agent shall be entitled to refrain
from any act or the taking of any action (including the failure to take an
action) in connection with this Security Agreement and the Notes or from the
exercise of any power, discretion or authority vested in him hereunder or
thereunder unless and until Collateral Agent shall have received instructions in
respect thereof from the Lenders (or such other Lenders as may be required to
give such instructions under Section 14 hereof) and, upon receipt of such
instructions from Lenders (or such other Lenders, as the case may be),
Collateral Agent shall be entitled to act or (where so instructed) refrain from
acting, or to exercise such power, discretion or authority, in accordance with
such instructions. Without prejudice to the generality of the foregoing, (i)
Collateral Agent shall be entitled to rely, and shall be fully protected in
relying, upon any communication, instrument or document believed by it to be
genuine and correct and to have been signed or sent by the proper person or
persons, and shall be entitled to rely and shall be protected in relying on
opinions and judgments of attorneys (who may be attorneys for Borrower and its
subsidiaries), accountants, experts and other professional advisors selected by
it; and (ii) no Lender shall have any right of action whatsoever against
Collateral Agent as a result of Collateral Agent acting or (where so instructed)
refraining from acting under this Security Agreement or the Notes in accordance
with the instructions of Lenders (or such other Lenders as may be required to
give such instructions under Section 14 hereof).

                  (d) REPRESENTATIONS AND WARRANTIES; NO RESPONSIBILITY FOR
APPRAISAL OF CREDITWORTHINESS. Each Lender agrees that he has made his own
independent investigation of the financial condition and affairs of Borrower and
its subsidiaries in connection with the making of the Loans hereunder and that
he has made and shall continue to make its own appraisal of the creditworthiness
of Borrower and its subsidiaries. Collateral Agent shall not have any duty or
responsibility, either initially or on a continuing basis, to make any such
investigation or any such appraisal on behalf of Lenders or to provide any
Lender with any credit or other information with respect thereto, whether coming
into its possession before the making of the Loans or at any time or times
thereafter, and Collateral Agent shall not have any responsibility with respect
to the accuracy of or the completeness of any information provided to Lenders.

                  (e) SUCCESSOR COLLATERAL AGENT. Collateral Agent may resign at
any time by giving thirty (30) calendar days prior written notice thereof to
Lenders and Borrower. Upon any such notice of resignation, Lenders shall have
the right, upon five (5) business days notice to Borrower, to appoint a
successor Collateral Agent, except during the continuation of a Default, with
the consent of Borrower (which consent shall not be unreasonably withheld or
delayed). If Lenders have not appointed a successor Collateral Agent by the date
set for Collateral Agent's resignation, Collateral Agent shall appoint such
successor Collateral Agent in consultation with Borrower. Upon the acceptance of
any appointment as Collateral Agent hereunder by a successor Collateral Agent,
that successor Collateral Agent shall thereupon succeed to and become vested
with all the rights, powers, privileges and duties of the retiring Collateral
Agent and the retiring Collateral Agent shall be discharged from its duties and
obligations under this Security Agreement. After any retiring Collateral Agent's
resignation hereunder as Collateral Agent, the provisions of this Section 11
shall inure to its benefit as to any actions taken or omitted to be taken by it
while it was Collateral Agent under this Security Agreement.

                                      -11-

<PAGE>

                  (f) RIGHT TO INDEMNITY. Each Lender, in proportion to the
percentage equivalent at such time of such Lender's aggregate unpaid principal
amount of the Lender's Loan, divided by the aggregate unpaid principal amount of
all Loans made by each Lender, severally agrees to indemnify Collateral Agent
and his employees, agents, attorneys, professional advisors and affiliates to
the extent that any such Person shall not have been reimbursed by Borrower
pursuant to the terms hereof, for and against any and all liabilities,
obligations, losses, damages, penalties, actions, judgments, suits, costs,
expenses (including counsel fees and disbursements and fees and disbursements of
any financial advisor engaged by Collateral Agent) or disbursements of any kind
or nature whatsoever which may be imposed on, incurred by or asserted against
Collateral Agent or such other Persons in exercising the powers, rights and
remedies of Collateral Agent or performing the duties of Collateral Agent
hereunder or under the other Loan Documents or otherwise in its capacity as
Collateral Agent in any way relating to or arising out of this Agreement or the
other Loan Documents; provided that no Lender shall be liable for any portion of
such liabilities, obligations, losses, damages, penalties, actions, judgments,
suits, costs, expenses or disbursements of Collateral Agent resulting from
Collateral Agent's gross negligence or willful misconduct. If any indemnity
furnished to Collateral Agent or other Persons for any purpose shall, in the
opinion of Collateral Agent, be insufficient or become impaired, Collateral
Agent may call for additional indemnity and cease, or not commence, to do the
acts indemnified against until such additional indemnity is furnished.

                  (g) COLLATERAL AGENT MAY FILE PROOFS OF CLAIM. In case of the
pendency of any receivership, insolvency, liquidation, bankruptcy,
reorganization, arrangement, adjustment, composition or other judicial
proceeding relative to Borrower or any of its subsidiaries, Collateral Agent
(irrespective of whether the principal of any Loan shall then be due and payable
as herein expressed or by declaration or otherwise and irrespective of whether
Collateral Agent shall have made any demand on Borrower) shall be entitled and
empowered, by intervention in such proceeding or otherwise;

                  (i) to file and prove a claim for the whole amount of
principal and interest owing and unpaid in respect of the Loans and any other
Secured Obligations that are owing and unpaid and to file such other papers or
documents as may be necessary or advisable in order to have the claims of
Lenders and Collateral Agent (including any claim for the reasonable
compensation, expenses, disbursements and advances of Lenders and Collateral
Agent and their agents and counsel and all other amounts due Lenders and
Collateral Agent hereunder) allowed in such judicial proceeding; and

                  (ii) to collect and receive any moneys or other property
payable or deliverable on any such claims and to distribute the same;

                                      -12-

<PAGE>

and any custodian, receiver, assignee, trustee, liquidator, sequestrator or
other similar official in any such judicial proceeding is hereby authorized by
each Lender to make such payments to Collateral Agent and, in the event that
Collateral Agent shall consent to the making of such payments directly to
Lenders, to pay to Collateral Agent any amount due for the reasonable
compensation, expenses, disbursements and advances of Collateral Agent and his
agents and counsel, and any other amounts due Collateral Agent hereunder.

                  Nothing herein contained shall be deemed to authorize
Collateral Agent to authorize or consent to or accept or adopt on behalf of any
Lender any plan of reorganization, arrangement, adjustment or composition
affecting the Secured Obligations or the rights of any Lenders or to authorize
Collateral Agent to vote in respect of the claim of any Lender in any such
proceeding.

                  SECTION 12. REMEDIES. If any Default shall have occurred, then
during the continuance of such Default, Collateral Agent may:

                  (a) Declare all Secured Obligations, whether evidenced by this
Security Agreement, the Notes, or otherwise, immediately due and payable
(provided, that upon the occurrence of a Default, all Secured Obligations shall
become immediately due and payable without any action by Collateral Agent);

                  (b) Terminate this Security Agreement as to any future
liability or obligation of any Lender, but without affecting the obligations of
Borrower to Lenders; and

                  (c) Exercise all rights and remedies of a secured party under
the UCC, subject to the subordination provisions contained in Section 6 of the
Notes. Without limiting the generality of the foregoing, Borrower expressly
agrees that in any such event Collateral Agent, without demand of performance or
other demand, advertisement or notice of any kind (except the notice specified
below of time and place of public or private sale) to or upon Borrower or any
other person (all and each of which demands, advertisements and notices are
hereby expressly waived to the maximum extent permitted by the UCC and other
applicable law), may (i) reclaim, take possession, recover, store, maintain,
finish, repair, prepare for sale or lease, shop, advertise for sale or lease and
sell or lease (in the manner provided herein) the Collateral, and in connection
with the liquidation of the Collateral and collection of the accounts receivable
pledged as Collateral, and (ii) forthwith collect, receive, appropriate and
realize upon the Collateral, or any part thereof, and may forthwith sell, lease,
assign, give an option or options to purchase or sell or otherwise dispose of
and deliver said Collateral (or contract to do so), or any part thereof, in one
or more parcels at public or private sale or sales, at any exchange or broker's
board or at Collateral Agent's offices or elsewhere at such prices as it may
deem best, for cash or on credit or for future delivery without assumption of
any credit risk. To the extent Borrower has the right to do so, Borrower
authorizes Collateral Agent, on the terms set forth in this Section 12 to enter
the premises where the Collateral is located, to take possession of the
Collateral, or any part of it, and to pay, purchase, contact, or compromise any
encumbrance, charge, or Lien which, in the opinion of Collateral Agent, appears
to be prior or superior to its security interest. Collateral Agent shall have
the right upon any such public sale or sales, and, to the extent permitted by
law, upon any such private sale or sales, to purchase the whole or any part of
said Collateral so sold, free of any right or equity of redemption, which equity
of redemption Borrower hereby releases. Borrower further agrees, at Collateral
Agent's request, to assemble its Collateral and make it available to Collateral
Agent at places which Collateral Agent shall reasonably select, whether at
Borrower's premises or elsewhere. Collateral Agent shall apply the net proceeds

                                      -13-

<PAGE>

of any such collection, recovery, receipt, appropriation, realization or sale as
provided in subsection (e) below and only after so paying over such net proceeds
and after the payment by Collateral Agent of any other amount required by any
provision of law, need Collateral Agent account for the surplus, if any, to
Borrower. To the maximum extent permitted by applicable law, Borrower waives all
claims, damages, and demands against Collateral Agent arising out of the
repossession, retention or sale of the Collateral. Collateral Agent shall give
Borrower at least ten (10) calendar days notice of the time and place of any
public sale or private sale may take place and such notice shall be deemed
reasonable notification of such matters. Borrower shall remain liable for any
deficiency if the proceeds of any sale or disposition of its Collateral are
insufficient to pay all amounts to which Collateral Agent is entitled from
Borrower, Borrower also being liable for the attorney costs of any attorneys
employed by Collateral Agent to collect such deficiency

                  (d) Borrower agrees that in any sale of any Collateral,
whether at a foreclosure sale or otherwise, Collateral Agent is hereby
authorized to comply with any limitation or restriction in connection with such
sale as it may be advised by counsel is necessary in order to avoid any
violation of applicable law (including compliance with such procedures as may
restrict the number of prospective bidders and purchasers, require that such
prospective bidders and purchasers have certain qualifications and restrict such
prospective bidders and purchasers to persons who will represent and agree that
they are purchasing for their own account for investment and not with a view to
the distribution or resale of such Collateral), or in order to obtain any
required approval of the sale or of the purchaser by any government authority,
and Borrower further agrees that such compliance shall not result in such sale
being considered or deemed not to have been made in a commercially reasonable
manner, nor shall Collateral Agent be liable nor accountable to Borrower for any
discount allowed by the reason of the fact that such Collateral is sold in
compliance with any such limitation or restriction.

                  (e) The proceeds of any sale, disposition or other realization
upon all or any part of the Collateral shall be distributed by Collateral Agent
in the following order of priorities:

                       (1) to Collateral Agent in an amount sufficient to pay in
full the reasonable costs of Collateral Agent in connection with such sale,
disposition or other realization, including all fees, costs, expenses,
liabilities and advances incurred or made by Collateral Agent in connection
therewith, including, without limitation, reasonable attorneys' fees;

                       (2) to the Lenders in amounts proportional to each
Lender's pro rata share of the then unpaid Secured Obligations; and

                       (3) upon payment in full of the Secured Obligations, to
Borrower or its representatives, in accordance with the UCC or as a court of
competent jurisdiction may direct.

                  SECTION 13. INDEMNITY AND EXPENSES.

                  (a) Borrower agrees to defend, indemnify and hold harmless the
Lenders and their employees and agents against (i) all obligations, demands,
claims, and liabilities claimed or asserted by any other party in connection
with the transactions contemplated by this Security Agreement and (ii) all
losses or expenses in any way suffered, incurred, or paid by any Lender as a

                                      -14-

<PAGE>

result of or in any way arising out of the transactions contemplated hereby
(including without limitation, reasonable attorneys' fees and expenses), except
for losses arising from or out of the gross negligence or willful misconduct of
Lenders.

                  (b) Borrower will upon demand pay to the Collateral Agent the
amount of any and all reasonable expenses, including the fees and out of pocket
disbursements of its counsel and of any experts and agents, which the Collateral
Agent may incur in connection with (i) the custody, preservation, use or
operation of, or the sale of, collection from, or other realization upon, any of
the Collateral contemplated by this Security Agreement and any related
documents, and (ii) the interpretation, performance or enforcement of any of the
rights of the Collateral Agent. All amounts payable by Borrower under this
Section 13(b) shall be paid together with interest thereon, from the date
incurred by the Collateral Agent or the Lenders until paid, calculated on the
basis of a year of 365 days and for the actual number of days elapsed, at the
highest rate of interest then applicable to any of the Secured Obligations.

                  SECTION 14. AMENDMENTS AND WAIVERS. No amendment,
modification, termination or waiver of any provision of this Security Agreement,
and no consent to any departure by Borrower therefrom, shall in any event be
effective without the written consent of the Lenders; provided that no such
amendment, modification, termination, waiver or consent shall, without the
written consent of each Lender with Secured Obligations directly affected (a)
reduce the principal amount of any Loan, (b) postpone the date or reduce the
amount of any scheduled payment (but not prepayment) of principal of any Loan,
(c) postpone the date on which any interest is payable, (d) decrease the
interest rate borne by any Loan, (e) change in any manner any provision of this
Security Agreement that, by its terms, expressly requires the approval or
consent of all Lenders, (f) release any Lien granted in favor of Collateral
Agent with respect to all or substantially all of the Collateral other than in
accordance with the terms of this Security Agreement, or (g) change in any
manner or waive the provisions contained in this Section 14. In addition, (x) no
amendment, modification, termination or waiver of any provision of any Note
shall be effective without the written consent of the Lender which is the holder
of that Note, (y) no amendment, modification, termination or waiver of any
provision of Section 11 hereof or of any other provision of this Security
Agreement which, by its terms, expressly requires the approval or consent of
Collateral Agent shall be effective without the written consent of Collateral
Agent, and (z) no amendment, modification, termination or waiver of any
provision hereof that has the effect of changing any scheduled payments or
voluntary or mandatory prepayments shall be effective without the written
consent of Lenders. Any waiver or consent shall be effective only in the
specific instance and for the specific purpose for which it was given.
Collateral Agent may, but shall have no obligation to, with the written consent
of any Lender, execute amendments, modifications, waivers or consents on behalf
of that Lender. Any amendment, modification, termination, waiver or consent
effected in accordance with this Section 14 shall be binding upon each Lender at
the time outstanding, each future Lender and, if signed by Borrower, on
Borrower.

                  SECTION 15. NOTICES. All notices and other communications
required or permitted hereunder shall be in writing and shall be (i) mailed by
registered or certified mail, postage prepaid, (ii) delivered by reliable
overnight courier service, or (iii) otherwise delivered by hand or by messenger,
addressed, if to the Collateral Agent, to:

                                      -15-

<PAGE>

                           Darin A. Peterson
                           21 Flagstone
                           Coto de Caza, CA 92679

with a copy to:

                           Cooley Godward LLP
                           4401 Eastgate Mall
                           San Diego, CA 92121
                           Attention:       Frederick T. Muto, Esq.
                                            Deyan P. Spiridonov, Esq.
                           Facsimile:  (858) 550-6420

if to Borrower, to:

                           Allion Healthcare, Inc.
                           33 Walt Whitman Road
                           Suite 200A
                           Huntington Station, NY  11746
                           Attention:  Michael P. Moran
                           Facsimile:  (631) 547-6532

with a copy to:            McDermott, Will & Emery
                           50 Rockefeller Plaza
                           New York, NY  10020
                           Attention:  Harvey Z. Werblowsky, Esq.
                           Facsimile:  (212) 547-5444

or at such other address as the parties hereto shall have furnished to one
another in writing. All such notices and communications shall be effective upon
receipt.

SECTION 16. CONTINUING SECURITY INTEREST; TERMINATION; RELEASE. This Security
Agreement shall create a continuing security interest in the Collateral and
shall (a) remain in full force and effect until payment in full of the Secured
Obligations or upon the occurrence of the L/C Substitution as contemplated by
Section 2(b) hereof, (b) be binding upon Borrower, its successors and assigns,
and (c) inure to the benefit of the Collateral Agent and its successors. Upon
the payment in full of the Secured Obligations or the occurrence of the L/C
Substitution, the security interest granted hereby shall automatically terminate
and all rights to the Collateral shall revert to Borrower. After such
termination, at the request and expense of Borrower, the Collateral Agent and
each Lender shall promptly execute and deliver to Borrower the proper
instruments (including Uniform Commercial Code termination statements on Form
UCC-3) acknowledging the termination of this Security Agreement, and will duly
assign, transfer and deliver to Borrower (without recourse and without any
representation or warranty) such of the Collateral as may be in the possession
of the Collateral Agent and each Lender shall promptly as has not theretofore
been sold or otherwise applied or released pursuant to this Security Agreement.
Unless Borrower shall have provided the letter of credit specified in Section
2(b) hereof, should Borrower become insolvent or make an assignment for the

                                      -16-

<PAGE>

benefit of creditors or should a receiver or trustee be appointed for all or any
significant part of Borrower's property and assets, this Security Agreement
shall continue to be effective or be reinstated, as the case may be, if at any
time payment and performance of the Secured Obligations, or any part thereof,
is, pursuant to applicable law, rescinded or reduced in amount, or must
otherwise be restored or returned by any obligee of the Secured Obligations,
whether as a "voidable preference," "fraudulent conveyance," or otherwise, all
as though such payment or performance had not been made. In the event that any
payment, or any part thereof, is rescinded, reduced, restored or returned, the
Secured Obligations shall be reinstated and deemed reduced only by such amount
paid and not so rescinded, reduced, restored or returned.

                  SECTION 17. GOVERNING LAW; TERMS. This Security Agreement
shall be governed by and construed in accordance with the laws of the State of
California, except to the extent that the validity or perfection of the security
interest hereunder, or remedies hereunder, in respect of any particular
Collateral are governed by the laws of a jurisdiction other than the State of
California. Unless otherwise defined herein, in the Notes or in the Purchase
Agreement, terms used in Article 9, as in effect on the date hereof, of the
Uniform Commercial Code of the State of California are used herein as therein
defined.

                  SECTION 18. WAIVER OF JURY TRIAL. BORROWER AND LENDERS EACH
HEREBY WAIVE THE RIGHT TO TRIAL BY JURY IN ANY ACTION OR PROCEEDING BASED UPON,
ARISING OUT OF, OR IN ANY WAY RELATING TO, THIS SECURITY AGREEMENT, THE LOAN
DOCUMENTS OR ANY OTHER PRESENT OR FUTURE INSTRUMENT OR AGREEMENT BETWEEN LENDERS
AND BORROWER RELATED HERETO OR THERETO, OR ANY CONDUCT, ACTS OR OMISSIONS OF
LENDERS OR BORROWER OR ANY OF THEIR DIRECTORS, OFFICERS, EMPLOYEES, AGENTS,
ATTORNEYS OR ANY OTHER PERSONS AFFILIATED WITH LENDERS OR BORROWER, IN ALL OF
THE FOREGOING CASES, WHETHER SOUNDING IN CONTRACT OR TORT OR OTHERWISE. THIS
WAIVER IS A MATERIAL INDUCEMENT FOR ALL PARTIES TO ENTER INTO THIS AGREEMENT.
EACH PARTY HAS REVIEWED THIS WAIVER WITH ITS COUNSEL.

                  SECTION 19. MISCELLANEOUS. This Security Agreement is in
addition to and not in limitation of any other rights and remedies Collateral
Agent may have by virtue of any other instrument or agreement heretofore,
contemporaneously herewith or hereafter executed by Borrower or by law or
otherwise. If any provision of this Security Agreement is contrary to applicable
law, such provision shall be deemed ineffective without invalidating the
remaining provisions hereof. If and to the extent that applicable law confers
any rights in addition to any of the provisions of this Security Agreement, the
affected provision shall be considered amended to conform thereto. The
Collateral Agent shall not by any act, delay, omission or otherwise be deemed to
have waived any of its rights or remedies hereunder. This Security Agreement may
be executed in any number of counterparts, all of which taken together shall
constitute one and the same instrument and the parties hereto may execute this
Security Agreement by signing any such counterpart.

                                      -17-

<PAGE>

                  IN WITNESS WHEREOF, the parties hereto have caused this
Security Agreement to be duly executed and delivered as of the date first above
written.

                                 BORROWER:
                                 ---------

                                 ALLION HEALTHCARE, INC.

                                 By:
                                      -----------------------------------------
                                      Michael P.  Moran
                                      President and Chief Executive Officer

                                 LENDERS:
                                 --------

                                      Darin A. Peterson, individually

                                      Allan H. Peterson, individually

                                 COLLATERAL AGENT:
                                 ----------------

                                 By:_______________________________________
                                      Darin A. Peterson

<PAGE>

                                   SCHEDULE I
                              TO SECURITY AGREEMENT
                              ---------------------

                  Place of Business, Locations of Collateral, Permitted Liens,
Litigation

CHIEF PLACE OF BUSINESS
-----------------------
AND CHIEF EXECUTIVE OFFICE:
---------------------------

         33 Walt Whitman Road
         Suite 200A
         Huntington Station, NY 11746

LOCATIONS OF EQUIPMENT:
-----------------------

         N/A

LOCATIONS OF INVENTORY:
-----------------------

         Huntington Station, New York
         Austin, Texas
         Miami, Florida

LOCATION OF RECORDS EVIDENCING
------------------------------
ACCOUNTS RECEIVABLE AND OTHER COLLATERAL:
-----------------------------------------

         Same as above

PERMITTED LIENS
---------------

         Loans for borrowed money pursuant to the $6 million revolving term
credit facility under the Loan and Security Agreement by and among Borrower,
Mail Order Meds, Inc., Care Line of New York, Inc. and Heller Healthcare Finance
dated April 21, 1999 or any replacement of such facility

         Guaranty of $1,500,00 loan to Borrower by John Pappajohn

LITIGATION
----------

         None

<PAGE>

                                   SCHEDULE II
                              TO SECURITY AGREEMENT
                              ---------------------

                             Patents and Trademarks

1.   Patent Applications and Provisional Patent Applications (U.S. and Foreign)
     N/A

2.   Unregistered Trade Names Used by Borrower:
      MOMS Pharmacy
      Mail Order Meds of TX/DALLAS

                                      -2-

<PAGE>

                                  SCHEDULE III
                                  ------------
                              TO SECURITY AGREEMENT
                              ---------------------

                             Commercial Tort Claims

         N/AExhibit 10.2

                                                                  Execution Copy

                      SUBORDINATED SECURED PROMISSORY NOTE

$1,187,500.00                                                       May 1, 2003

                  FOR VALUE RECEIVED, the undersigned ALLION HEALTHCARE, INC., a
Delaware corporation (the "BORROWER"), promises to pay to DARIN A. PETERSON (the
"HOLDER"), the principal sum of ONE MILLION ONE HUNDRED EIGHTY-SEVEN THOUSAND
FIVE HUNDRED DOLLARS ($1,187,500.00), plus accrued interest from the date
hereof, at a rate equal to the Prime Rate, as published in the Eastern Edition
of The Wall Street Journal plus two percent (2%) per annum (the "INTEREST
RATE"), on the unpaid principal amount outstanding hereunder from time to time.
The Interest Rate shall be reset on each Payment Date (as defined below) and
shall apply for the following payment period. Payments of principal and interest
shall be made in lawful money of the United States of America, to the address of
record of the Holder as set forth herein, or at such place as the Holder may
designate in writing. This Subordinated Secured Promissory Note (this "NOTE") is
issued in connection with that certain Stock Purchase Agreement (as modified and
amended from time to time, the "PURCHASE AGREEMENT"), of even date herewith, by
and among the Borrower, the Holder, and Allan H. Peterson. The obligations of
the Borrower under this Note are secured by certain assets of Borrower as set
forth in that certain Subordinated Security Agreement (as modified and
supplemented from time to time, the "SECURITY AGREEMENT"), of even date
herewith, by and among the Borrower, the Holder, Allan H. Peterson and Darin A.
Peterson, as collateral agent. Capitalized terms used and not otherwise defined
herein shall have the same meanings ascribed to them in the Security Agreement.
In the event of a conflict between the terms hereof and the terms of the
Security Agreement, the terms of the Security Agreement shall prevail.

                  Subject to Section 6(g) hereof, principal and interest on this
Note shall be due and payable as follows:

                  (i)      The entire unpaid balance of the principal shall be
                           due and payable on the date that is two (2) years
                           from the date hereof (the "MATURITY DATE");

                  (ii)     Beginning on the date hereof until the Maturity Date,
                           interest on the outstanding principal amount shall be
                           due and payable in arrears on a quarterly basis on
                           each of June 30, 2003, September 30, 2003, December
                           31, 2003, March 31, 2004, June 30, 2004, September
                           30, 2004, December 31, 2004, and March 31, 2005 (each
                           a "PAYMENT DATE"). All computations of interest
                           payable hereunder shall be on the basis of a 365-day
                           year and actual days elapsed in the period of which
                           such interest is payable; and

                  (iii)    In the event that prior to the Maturity Date,
                           Borrower engages in (a) any underwritten public
                           offering of any shares of Borrower's capital stock
                           resulting in aggregate proceeds to Borrower in excess
                           of $25 million or (b) a Borrower Acquisition
                           Transaction, as herein defined, shall have occurred,
                           all outstanding payments due under this Note shall
                           become due and payable within thirty (30) calendar
                           days of the consummation of such underwritten public
                           offering or Borrower Acquisition Transaction, as the

<PAGE>

                           case may be (an "EARLY MATURITY DATE"). For purposes
                           of this Note, "BORROWER ACQUISITION TRANSACTION"
                           shall mean (x) any sale, lease, exchange, transfer or
                           other disposition of the assets of Borrower or any
                           subsidiary of Borrower constituting more than fifty
                           percent (50%) of the consolidated assets of Borrower
                           or accounting for more than fifty percent (50%) of
                           the consolidated revenues of Borrower in any one
                           transaction or in a series of related transactions,
                           or (y) any offer to purchase, tender offer, exchange
                           offer or any similar transaction or series of related
                           transactions made by any person or entity involving
                           more than fifty (50%) of the outstanding shares of
                           the capital stock of the Borrower or (z) any merger,
                           consolidation or similar transaction to which
                           Borrower is a party, other than (a) any merger
                           effected solely to implement a recapitalization of
                           the Borrower in which no person acquires more than
                           50% of the combined voting power of the Borrower's
                           then outstanding securities, or (b) any merger,
                           consolidation or similar transaction between or among
                           the Borrower and any of its then wholly-owned
                           subsidiaries.

                  (iv)     In the event that any indemnification claim by the
                           Borrower pursuant to the terms and conditions of the
                           Purchase Agreement is pending at the time of the
                           Early Maturity Date or the Maturity Date, the lesser
                           of (a) the amount of such claim and (b) the sum of
                           the outstanding principal and all accrued but unpaid
                           interest on this Note, shall be placed in a third
                           party escrow account mutually acceptable to Borrower
                           and Holder until the time that such pending claim is
                           resolved.

                  1. DEFAULT. In the case of the occurrence of one or more of
the following events (each, a "DEFAULT"): (i) the Borrower fails to make when
due any payment of principal or interest hereunder and such default is not cured
within five (5) calendar days; (ii) the Borrower becomes insolvent or generally
fails to pay, or admits in writing its inability to pay, any of its debts as
they become due; (iii) the Borrower applies for a trustee, receiver or other
custodian for it or a substantial part of its property; (iv) a trustee, receiver
or other custodian is appointed for the Borrower or for a substantial part of
its property; (v) any bankruptcy, reorganization, debt arrangement, or other
case or proceeding is commenced in respect of the Borrower; (vi) any
representation or warranty made by the Borrower in the Security Agreement or in
any certificate, financial statement or other document furnished pursuant
thereto shall prove to have been materially incorrect when made or (vii) (A)
Borrower breaches any of the covenants set forth in Sections 6(d) through (g),
inclusive, or Section 9 of the Security Agreement, (B) any default in the
observance or performance of any of the other conditions, covenants or
agreements of Borrower set forth herein or in the Security Agreement (other than
as set forth above), and continuance thereof for a period of ten (10) calendar
days after the Collateral Agent delivers written notice of such default to
Borrower (or such other cure period which may otherwise be applicable); or
(viii) any default in any agreement between Borrower and a third party that
gives the third party the right to accelerate the payment of $100,000 or more of
any indebtedness owed to the third party under such agreement, unless disputed
in good faith; then, upon the occurrence of any such event, all unpaid
principal, accrued interest and other amounts owing hereunder shall, at the
option of the Holder, and in the case of an event of default pursuant to (ii)
through (v) above, automatically, be immediately due, payable, and collectible
by Holder pursuant to applicable law. Failure to exercise this option shall not
constitute a waiver of the right to exercise the same at any other time.

                                      -2-

<PAGE>

                  2. DEFAULT INTEREST. Upon the occurrence and the continuance
of a Default, any amount of principal not paid before the due date shall accrue
interest at a rate per annum equal to the Interest Rate plus five percent (5%)
per annum.

                  3. WAIVER. Borrower hereby waives, to the fullest extent
permitted by applicable law, notice, demands, notice of nonpayment, presentment,
protest and notice of dishonor.

                  4. ENFORCEMENT. Upon the occurrence of a Default, the Holder
may employ an attorney to enforce the Holder's rights and remedies and the
Borrower hereby agrees to pay to the Holder's reasonable attorneys' fees, plus
all other reasonable expenses incurred by the Holder in exercising any of the
Holder's rights and remedies upon default. The rights and remedies of the Holder
as provided in this Note shall be cumulative and may be pursued singly,
successively, or together against any other funds, property or security held by
the Holder for payment or security, in the sole discretion of the Holder. The
failure to exercise any such right or remedy shall not be a waiver or release of
such rights or remedies or the right to exercise any of them at another time.

                  5. SUBORDINATION. The indebtedness evidenced by this Note is
hereby expressly subordinated, to the extent and in the manner hereinafter set
forth, in right of payment to the prior payment in full of the Senior
Indebtedness. For purposes hereof, "SENIOR INDEBTEDNESS" shall mean, unless
expressly subordinated to or made on a parity with the amounts due under this
Note, the principal of, unpaid interest on and amounts reimbursable, fees,
expenses, costs of enforcement by (x) wholesalers in the ordinary course of
business and (y) any lender for borrowed money (each, a "SENIOR LENDER")
pursuant to the $6 million revolving term credit facility under the Loan and
Security Agreement by and among Borrower, Mail Order Meds, Inc., Care Line of
New York, Inc. and Heller Healthcare Finance dated April 21, 1999 or any
replacement of such facility. By acceptance of this Note, Holder hereby
authorizes the Collateral Agent to execute and deliver, on Holder's behalf,
customary forms of subordination agreement requested from time to time by the
Senior Lender. The Holder shall enter into such subordination agreements
consistent with the provisions of this Section 5 as may be reasonably requested
by the Senior Lender.

                  6. MISCELLANEOUS. The following general provisions apply:

                  (a) This Note, and the obligations and rights of the parties
hereunder, shall be binding upon and inure to the benefit of the Borrower, the
Holder, and their respective heirs, personal representatives, successors and
assigns.

                  (b) Changes in or amendments or additions to this Note may be
made, or compliance with any term, covenant, agreement, condition or provision
set forth herein may be omitted or waived (either generally or in a particular
instance and either retroactively or prospectively), upon written consent of the
Borrower and the Holder.

                                      -3-

<PAGE>

                  (c) The undersigned and any holder hereof waive trial by jury
in any action or proceeding to which the undersigned and any such holder may be
parties arising out of or in connection with this Note.

                  (d) In the event that the rate of interest provided for in
this Note exceeds the maximum rate permitted by law, such rate of interest shall
be reduced to the maximum rate of interest permitted by law.

                  (e) All notices, requests, consents and demands shall be made
in writing and shall be mailed postage prepaid, or delivered by reliable
overnight courier or by hand, to the Borrower or to the Holder at their
respective addresses set forth below or to such other address as may be
furnished in writing to the other party hereto and shall be effective upon
receipt:

                  If to the Borrower, at 33 Walt Whitman Road, Suite 200A,
Huntington Station, NY 11746, Attention: Chief Executive Officer.

                  If to the Holder, at 21 Flagstone, Coto de Caza, CA, 92679.

                  (f) This Note shall be construed and enforced in accordance
with, and the rights of the parties shall be governed by, the laws of the State
of California.

                  (g) Notwithstanding anything contained herein to the contrary,
Borrower has the right to set off amounts due to the Holders under this Note
against any purchase price adjustment and/or indemnification obligations that
the Holders have to Borrower pursuant to Section 1.7 or Article 9 of the
Purchase Agreement.

                  IN WITNESS WHEREOF, the Borrower has caused this Note to be
executed in its corporate name by a duly authorized officer, by order of its
Board of Directors as of the day and year first above written.

                                 ALLION HEALTHCARE, INC.

                                 By:
                                      -------------------------------------
                                      Name:  Michael P.  Moran
                                      Title: President and
                                             Chief Executive Officer

                                      -4-

<PAGE>

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