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                                                                    Exhibit 10.4

                      CODEVELOPMENT AND LICENSING AGREEMENT

       THIS CODEVELOPMENT AND LICENSING AGREEMENT (referred to hereinafter as
this "Agreement") is entered into this 21st day of June, 1999 by and between:

              TEIJIN LIMITED (a corporation duly organized under
              the laws of Japan and having its registered office
              and principal place of business at 6-7,
              Minami-honmachi 1-chome, Chuo-ku, Osaka 541, Japan)
              and its successors, subsidiaries, and assigns
              (hereinafter referred to as "Teijin")

                                       and

              AKSYS, LTD. (a corporation duly organized under the
              laws of the State of Delaware, USA, and having its
              principal place of business at 2 Marriott Drive,
              Lincolnshire, Illinois 60069, USA) and its
              successors, subsidiaries, and assigns (hereinafter
              referred to as "Aksys")

                                    RECITALS

       WHEREAS, Teijin provides medical devices and equipment, drugs, and
related services in Japan which are used for the treatment at home of patients
requiring oxygen and also provides other therapies and has developed a unique
and substantial capability to support the treatment of seriously ill patients at
home;

       WHEREAS, Teijin desires to utilize and expand the aforesaid capability by
introducing products for the treatment at home (and possibly in other
non-traditional locations) of patients requiring hemodialysis;

       WHEREAS, Aksys is developing an automated hemodialysis system which is
uniquely suited to supporting patients at home (and possibly in other
non-traditional locations) and will soon complete the initial version of such
system; and

       WHEREAS, Teijin and Aksys intend to collaborate, and have already begun
to collaborate, in developing a substantially improved version of the aforesaid
system which is to be manufactured and marketed both in the United States (by
Aksys beginning in 2001) and in Japan (by Teijin beginning in 2002);

       NOW THEREFORE, in consideration of the mutual covenants and premises
herein contained and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, accepted and agreed to, Teijin and
Aksys, intending to be legally bound, hereby agree as follows.

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                             ARTICLE 1: DEFINITIONS

       For purposes of this Agreement, the following terms (when used herein
with initial capital letters) shall have the respective meanings specified or
referred to in this Article 1:

1.1.   MHW: The term "MHW" shall mean the Japanese Ministry of Health and
Welfare and other agencies through which submissions are made to the Japanese
Ministry of Health and Welfare including, for example and without limitation,
the Tokyo Metropolitan Government (i.e. TOCHO) and the Japan Association for the
Advancement of Medical Equipment (i.e. IRYO KIKI CENTER).

1.2.   IMPORT APPROVAL: The term "Import Approval" (i.e. YUNYU SHONIN) shall
mean the approval granted by the MHW to import a drug or medical device for sale
in Japan.

1.3.   MANUFACTURING APPROVAL: The term "Manufacturing Approval" (i.e. SEIZO
SHONIN) shall mean the approval granted by the MHW to manufacture a drug or
medical device for sale in Japan.

1.4.   APPROVAL: The term "Approval" (i.e. SHONIN) shall refer to either
Manufacturing Approval, Import Approval, or both, as defined herein.

1.5.   AKSYS APPROVAL DATE: The term "Aksys Approval Date" shall mean the date
on which the MHW first grants an Approval to Aksys for any of the Products.

1.6.   SYSTEM: The term "System" shall mean Aksys' PHD(TM) Personal Hemodialysis
System, including any and all versions thereof and improvements and
modifications thereto which are existing during the Term of this Agreement and
prior to the Aksys Approval Date.

1.7.   VERSION C: The term "Version C" shall mean that version of the System
which shall be jointly developed by Aksys and Teijin in accordance with Article
3 hereof.

1.8.   PRODUCTS: The term "Products" shall mean all permanent, disposable,
consumable and other items which comprise or are used in conjunction with the
System.

1.9.   TECHNOLOGY: The term "Technology" shall mean inventions, works of
authorship and other intellectual property, whether or not patentable,
copyrightable or subject to other forms of protection, and wherever developed,
protected or maintained, which are existing during the Term of this Agreement
and prior to the Aksys Approval Date and which are related and necessary to the
design, development, manufacture, use, promotion, marketing, distribution,
lease, rent, offer for sale, or sale of the Products. The term "Technology"
shall not include any trade name, trade dress, trademark, service mark or
similar symbols identifying a party or any intellectual property concerning
semiconductor materials, semiconductor manufacturing processes, methods or
techniques except as specifically identified in this or another agreement in
writing by the parties.

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1.10.  AKSYS TECHNOLOGY: The term "Aksys Technology" shall mean and include
Technology which: (i) is owned or controlled by Aksys or (ii) can be sublicensed
by Aksys to Teijin without additional cost to Aksys.

1.11.  TEIJIN TECHNOLOGY: The term "Teijin Technology" shall mean and include
Technology which: (i) is owned or controlled by Teijin or (ii) can be
sublicensed by Teijin to Aksys without additional cost to Teijin.

1.12.  REIMBURSEMENT: The term "Reimbursement" shall mean any and all payment(s)
which health care providers and/or patients are entitled to receive under
Japan's medical insurance system with respect to any medical procedure which is
performed using the Products and/or with respect to the sale or use of the
Products PER SE.

1.13.  FIRST COMMERCIAL SALE: The term "First Commercial Sale" shall mean the
first time that a health care provider or patient in Japan agrees to purchase,
lease, rent or otherwise acquire a Product and then uses such Product in the
performance of a hemodialysis procedure for which the health care provider or
patient is entitled to receive any Reimbursement, or is otherwise compensated
for having performed or undergone such procedure.

1.14.  GROSS REVENUE: The term "Gross Revenue" shall mean all revenue of any
kind which accrues or is owed to Teijin during the Term of this Agreement and is
derived from or in any way related to the sale or use of the Products. Gross
Revenue shall not include any Japanese consumption tax (i.e. SHOHIZEI) collected
by Teijin.

1.15.  NET REVENUE: The term "Net Revenue" shall mean Gross Revenue minus any
portion of such Gross Revenue which: (i) will not be received by Teijin due to
discounts granted by Teijin to any unrelated customers or (ii) has been refunded
by Teijin to unrelated customers who have returned Products.

1.16.  TERRITORY: The term "Territory" shall mean Japan.

1.17.  FDA: The term "FDA" shall mean the Food and Drug Administration of the US
Department of Health and Human Services.

1.18.  EFFECTIVE DATE: The term "Effective Date" shall mean the date of the last
signature hereto, as entered on the first page of this Agreement.

1.19.  AKSYS LAUNCH DATE: The term "Aksys Launch Date" shall mean the date on
which any Product for which the MHW has granted an Approval to Aksys is first
purchased, leased, rented, or

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otherwise obtained by a healthcare provider or patient in the Territory.

1.20.  ROYALTY DATE: The term "Royalty Date" shall mean the date on which the
cumulative amount of Teijin's Net Revenue has reached the amount of Twenty-four
Billion Japanese Yen (Y 24,000,000,000).

                          ARTICLE 2: TERM; TERMINATION

2.1.   TERM: This Agreement shall be effective from the Effective Date until
terminated in accordance with this Article 2 (the "Term" of this Agreement).

2.2    TERMINATION BY EITHER PARTY: After the tenth (10th) anniversary of the
First Commercial Sale, either party may terminate this Agreement, effective upon
receipt by the other party of written notice thereof.

2.3.   TERMINATION PURSUANT TO BREACH: In the event that either party, at any
time during the Term of this Agreement, commits a material breach of any
provision hereof, and fails to rectify such material breach within sixty (60)
days following receipt from the other party of written notice that such a
material breach has been committed, then such other party may terminate this
Agreement forthwith by giving written notice to the breaching party. Such
termination shall not prejudice any cause of action or claim of such other
party.

2.4.   TERMINATION EFFECT: Articles 1, 8, 10, 11, 12, and 13 hereof shall
survive termination of this Agreement. Upon termination of this Agreement, the
parties shall discuss in good faith and seek to determine the terms and
conditions (if any) under which either party may use the Technology owned by the
other party.

                      ARTICLE 3: CODEVELOPMENT OF VERSION C

3.1.   BACKGROUND: Aksys has been developing the System and will soon complete
the initial version of the System ("Version A"). Using Version A Aksys intends
to conduct clinical trials, obtain 510 (k) clearance, and begin to market the
System in the United States and Europe. However Aksys and Teijin both recognize
that Version A will be rather costly to manufacture and maintain and, therefore,
that it could be difficult for either party to establish a profitable business
using Version A.

3.2.   OBJECTIVES: The activities undertaken by the parties pursuant to this
Article 3 are intended to develop a new, commercially viable, version of the
System (i.e. "Version C"). Compared to Version A, Version C will be less costly
to manufacture and maintain, and it will incorporate such additional
improvements as may be determined and agreed to by the parties. It is intended
that Version C will replace Version A in the US and Europe beginning in 2001
and, furthermore, that Teijin will begin to manufacture and market Version C in
Japan beginning in 2002. In order to

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obtain the necessary Approval(s) for Version C by that time, Teijin intends to
conduct clinical trials in Japan beginning in the middle of 2000 and, therefore,
it is intended that samples of Version C which are sufficient for the
performance of such clinical trials be available by mid-2000. Prior to
conducting such clinical trials, Teijin will require samples of Version C for
pre-clinical testing and, therefore, it is intended that at least three samples
of Version C which are sufficient for the performance of such pre-clinical
testing be available by the second calendar quarter of 2000.

3.3    CO-DEVELOPMENT PROGRAM: Version C shall be developed in accordance with
the objectives set forth in Article 3.2 hereof and in accordance with a program
plan to be jointly determined and agreed to by the parties. The program plan
shall include the milestones set forth on Exhibit A attached hereto, and each
such milestone shall be deemed to have been achieved when both parties have
acknowledged such achievement in writing. The parties shall jointly determine
and agree to each party's duties under the program plan. Each party shall
exercise its reasonable efforts to perform its duties under the program plan,
until the co-development program has been completed in accordance with Article
3.4 hereof.

3.4.   COMPLETION OF THE CO-DEVELOPMENT PROGRAM: Unless otherwise agreed by the
parties in writing, the co-development program for Version C shall continue
until the final milestone set forth on Exhibit A attached hereto (i.e. "Approval
for Shipment") has been achieved.

3.5.   RIGHT TO ATTEND BOARD MEETINGS: Until the co-development program for
Version C has been completed in accordance with Article 3.4 hereof, an
individual named by Teijin shall have the right (but not the obligation) to
attend those portions of the regular meetings of the Aksys Board of Directors
which are related to the discussion and review of Aksys' product development
activities.

                         ARTICLE 4: DEVELOPMENT EXPENSES

4.1.   AKSYS DEVELOPMENT EXPENSES FUNDED BY TEIJIN: Upon receipt from Teijin of
the payment specified in Article 7.1 hereof, Aksys shall establish a budget in
the amount of Seven Million US Dollars ($7,000,000). Near the end of June, 1999
and near the end of each calendar quarter thereafter, until Aksys has spent all
of the aforesaid budget, Aksys shall provide Teijin with reports showing Aksys'
actual spending to date against this budget, and the amount of this budget which
remains unspent. Until such time as the co-development program for Version C has
been completed in accordance with Article 3.4 hereof, the actual expenditures
presented in such reports shall include only expenditures which are related and
necessary to the performance of Aksys' duties under Article 3.3 hereof, and
shall not include expenditures solely related to the development of Version A.
After the co-development program for Version C has been completed in accordance
with Article 3.4 hereof, the actual expenditures presented in such reports may
include items which are necessary and related to development of the System, but
which are not specifically related to Version C. Aksys shall exercise reasonable
efforts to ensure that its spending is sufficient for the timely completion of
its duties under Article 3.3 hereof and, also, to ensure that Teijin understands
how and why such funds are being spent. Aksys shall comply with Teijin's
reasonable requests for additional

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explanation, information, and supporting data.

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4.2.   OTHER DEVELOPMENT EXPENSES: Except as provided in Article 4.1 hereof,
neither party shall be obligated to reimburse any costs or expenses which the
other party incurs in connection with the performance of its duties under
Article 3 hereof. Each party shall be solely responsible for: (i) all salary,
benefits, and other compensation paid to its own employees and contractors,
(ii) all transportation, lodging, meals, and other expenses incurred by its own
employees and contractors, (iii) all costs and expenses which it incurs to
establish, maintain, equip, and operate its own facilities, and (iv) all other
costs and expenses which it incurs to support development activities which take
place in its own facilities.

4.3.   REGULATORY EXPENSES. Article 4.2. notwithstanding, each party shall be
solely responsible for all costs and expenses related to obtaining any
regulatory approvals which are required prior to beginning its own manufacturing
and marketing activities, including without limitation the cost of any samples
required to perform preclinical or clinical testing for purposes of obtaining
such approval. Should one party request assistance from the other party in
obtaining regulatory approvals, then the party requesting such assistance shall
reimburse the other party for all costs and expenses reasonably incurred to
provide such assistance.

4.4.   MANUFACTURING AND MARKETING EXPENSES: Article 4.2. notwithstanding, each
party shall be solely responsible for all costs and expenses related to its own
manufacturing and marketing activities. Should one party request assistance from
the other party in establishing its own manufacturing and marketing
capabilities, then the party requesting such assistance shall reimburse the
other party for all costs and expenses reasonably incurred to provide such
assistance.

                       ARTICLE 5: RIGHTS IN THE TERRITORY

5.1.   TEIJIN'S RIGHT: During the Term of this Agreement, Teijin shall have the
exclusive right to develop, make, use, promote, market, distribute, lease, rent,
offer for sale, and sell the Products in the Territory; provided however that,
unless otherwise agreed by the parties in writing: (i) Aksys shall have the
option to develop, make, use, promote, market, distribute, lease, rent, offer
for sale, and sell the Products in the Territory, in accordance with Article 5.2
hereof; (ii) Teijin shall not develop, make, use, promote, market, distribute,
lease, rent, offer for sale, or sell the Products outside the Territory; and
(iii) Teijin shall not enable or assist any third-party to develop, make, use,
promote, market, distribute, lease, rent, offer for sale, or sell the Products,
except as provided in Articles 5.3 and 5.4 hereof.

5.2.   AKSYS' OPTION IN THE TERRITORY: During the Term of this Agreement, Aksys
shall have the option to develop, make, use, promote, market, distribute, lease,
rent, offer for sale, and sell the Products in the Territory; provided however
that, unless otherwise agreed by the parties in writing: (i) Aksys shall not
enable or assist any third-party to develop, make, use, promote, market,
distribute, lease, rent, offer for sale, or sell the Products in the Territory,
except as provided in Articles 5.3 and 5.4 hereof; (ii) Aksys shall not submit
an application to the MHW for an Approval for any of the Products until after
the earlier of the second (2nd) anniversary of the First Commercial Sale or

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December 31, 2005; (iii) at least ninety (90) days prior to submitting its first
application to the MHW for Approval of any of the Products, Aksys shall give
written notice thereof to Teijin; (iv) following the receipt by Teijin of such
notice, the parties shall discuss and amicably seek to address any regulatory,
reimbursement, commercial, or other issues which could arise if and when the MHW
grants such an Approval to Aksys; and (v) notwithstanding the nature or outcome
of the aforesaid discussions, upon being granted an Approval for any of the
Products, Aksys shall have the right to develop, make, use, promote, market,
distribute, lease, rent, offer for sale, and sell the Products in the Territory.

5.3.   CONTRACT MANUFACTURERS: This Agreement shall not prevent either party
from entering into agreements with contract manufacturers or other third-parties
in the Territory under which such third- parties will develop and/or make the
Products in the Territory; provided however, that neither party shall enter into
any such agreement without the prior written consent of the other party, which
consent shall not be unreasonably withheld.

5.4.   WHOLESALERS AND DISTRIBUTORS: This Agreement shall not prevent either
party from promoting, marketing, distributing, leasing, renting, offering for
sale, or selling the Products in the Territory through wholesalers and
distributors (i.e. DAIRITEN); provided however that: (i) neither party shall
enable or assist any third-party to obtain an Approval for any of the Products
and (ii) Teijin shall exercise its reasonable efforts to ensure that any
third-party which obtains the Products from Teijin shall not sell or otherwise
transfer the Products outside the Territory, to any party other than Aksys.

                     ARTICLE 6: RIGHTS OUTSIDE THE TERRITORY

       During the Term of this Agreement, Aksys shall have the exclusive right
to develop, make, use, promote, market, distribute, lease, rent, offer for sale,
and sell the Products outside the Territory. This Agreement shall not prevent
Aksys from entering into agreements of any kind with any third-parties outside
the Territory; provided however that Aksys shall exercise its reasonable efforts
to ensure that no third-party outside the Territory which obtains the Products
from Aksys shall sell or otherwise transfer the Products into the Territory, to
any party other than Aksys or Teijin.

                               ARTICLE 7: PAYMENTS

7.1.   RESEARCH AND DEVELOPMENT FUNDS: On the Effective Date of this Agreement,
Teijin will pay to Aksys the amount of Seven Million US Dollars (US$7,000,000)
as a non-refundable advance against expenditures to be made by Aksys in
accordance with Article 4.1 hereof.

7.2.   LICENSING FEE: On the Effective Date of this Agreement, in addition to
the payment made in accordance with Article 7.1 hereof, Teijin will pay to Aksys
the amount of Seven Million US Dollars (US$7,000,000) as a licensing fee.

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7.3.   ROYALTIES PAID TO AKSYS: After the Royalty Date, Teijin will pay
royalties to Aksys as follows:

       (i)    Teijin will pay to Aksys as royalties ten percent (10%) of the Net
              Revenue which Teijin earns after the Royalty Date and before the
              Aksys Launch Date.

       (ii)   Teijin will pay to Aksys as royalties five percent (5%) of the Net
              Revenue which Teijin earns after the Royalty Date and after the
              Aksys Launch Date.

       (iii)  Teijin will pay such royalties to Aksys within sixty (60) days
              following the end of each calendar quarter in which Net Revenue is
              earned.

       (iv)   Unless otherwise agreed by the parties in writing, all royalties
              will be paid to Aksys in US Dollars at the rate of exchange
              prevailing at the time such payment is made.

7.4.   POSSIBLE REDUCTION OF ROYALTY RATES: The royalty rates set forth in
Article 7.3 hereof may be reduced by mutual written consent of the parties.

7.5.   JAPANESE TAXES:

       (i)    ON SIGNATURE PAYMENTS: Notwithstanding Article 4.1 or any other
              provision of this Agreement, the payments made by Teijin in
              accordance with Articles 7.1 and 7.2 hereof, shall be
              non-refundable and payable without any set off or any deduction
              for Japanese taxes or withholding and to the extent any deductions
              or withholdings are required with respect to such payments, Teijin
              shall be solely responsible for any such payment, so that Aksys
              receives what it would have received absent any such deduction or
              withholding.

       (ii)   ON ROYALTY PAYMENTS: Should any withholding tax be levied by the
              fiscal authorities of Japan on royalty payments to be made by
              Teijin to Aksys under Article 7.3 hereof, then after having paid
              such withholding tax to the fiscal authorities of Japan, Teijin
              shall be entitled to deduct such withholding tax from payments to
              be made to Aksys hereunder. In such case, Teijin shall procure
              proper tax receipts and shall forward such tax receipts to Aksys
              in order to enable Aksys to obtain withholding tax credit. Should
              a tax exemption for withholding tax purposes be available under
              the laws of Japan or under any international tax treaty or similar
              agreement, then Teijin shall use commercially reasonable efforts
              to enable Aksys to obtain such exemption.

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                         ARTICLE 8: RIGHTS TO TECHNOLOGY

8.1.   TECHNOLOGY DEVELOPED BY TEIJIN: All Technology made in the performance of
any development solely by Teijin personnel shall be the sole and exclusive
property of Teijin and Teijin shall retain any and all rights to file any
applications for intellectual property rights thereon. Any and all such
technology shall be included in the definition of the term "Teijin Technology."
For the Term of this Agreement, Teijin hereby grants to Aksys a non-transferable
sole license, without the right to sublicense, to utilize Teijin Technology to
develop, make, have made, use, promote, market, distribute, lease, rent, offer
for sale and sell the Products worldwide.

8.2.   TECHNOLOGY DEVELOPED BY AKSYS: All Technology made in the performance of
any development solely by Aksys personnel shall be the sole and exclusive
property of Aksys and Aksys shall retain any and all rights to file any
applications for intellectual property rights thereon. Any and all such
technology shall be included in the definition of the term "Aksys Technology."
For the Term of this Agreement, Aksys hereby grants to Teijin a non-transferable
sole license, without the right to sublicense, to utilize Aksys Technology to
develop, make, have made, use, promote, market, distribute, lease, rent, offer
for sale and sell the Products in the Territory.

8.3.   TECHNOLOGY DEVELOPED JOINTLY BY TEIJIN AND AKSYS: All Technology made in
the performance of any development jointly by Teijin and Aksys personnel shall
be the property jointly of Teijin and Aksys ("Jointly Owned Technology"). In the
case of any Jointly Owned Technology, the parties shall mutually determine:
(i) whether an application or applications for intellectual property rights
should be filed, (ii) which party which will prepare, file, and prosecute such
application(s) (the "Filing Party"), and (iii) the country or countries in which
such application(s) shall be filed. Regardless of which party is the Filing
Party, all costs and expenses related to obtaining and defending intellectual
property rights for Jointly Owned Technology shall be borne equally by the
parties.

8.4.   ABANDONMENT OF JOINTLY OWNED TECHNOLOGY: Notwithstanding Article 8.3.
hereof, if either party declines to obtain, maintain, or defend any particular
intellectual property right for any Jointly Owned Technology or fails to pay its
share of the cost of obtaining, defending, or maintaining such intellectual
property right, then the party wishing to obtain and defend such intellectual
property right may do so independently, at its sole expense, and the other party
shall forthwith relinquish its right, title, and interest in such intellectual
property right.

                 ARTICLE 9: RIGHTS TO OBTAIN AND USE INFORMATION

9.1.   IN GENERAL: Prior to the Aksys Approval Date during the Term of this
Agreement, each party shall provide the other party with such documents,
information, and data related and necessary to the design, development,
manufacture, use, promotion, marketing, distribution, lease, rent, offer for
sale, or sale of the Products, as may be reasonably requested by the other
party, including without limitation as provided in this Article 9.

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9.2.   US REGULATORY DOCUMENTS, INFORMATION, AND DATA: Prior to the Aksys
Approval Date during the Term of this Agreement, and within thirty (30) days
following its submission to or receipt from the FDA of any document pertaining
to the Products, Aksys shall deliver a copy of each such document to Teijin.
Aksys shall comply with Teijin's reasonable requests to review information and
data supporting such documents, whether or not such information or data has been
submitted to the FDA.

9.3.   RESULTS OF US CLINICAL TRIALS: Prior to the Aksys Approval Date, during
the Term of this Agreement, Aksys will inform Teijin prior to beginning any
clinical trial which involves the use of the Products and provide Teijin with a
copy of the protocol to be used for each such trial. The results of such trials,
including information regarding adverse reactions or other problems which may
arise or be identified during the trial, will be reported to Teijin on a timely
basis. Aksys will comply with Teijin's reasonable requests for additional
information concerning such trials.

9.4.   JAPANESE REGULATORY DOCUMENTS, INFORMATION, AND DATA: Prior to the Aksys
Approval Date during the Term of this Agreement, and within thirty (30) days
following its submission to or receipt from the MHW of any document pertaining
to the Products, Teijin shall deliver a copy of each such document to Aksys.
Teijin shall comply with Aksys' reasonable requests to review information and
data supporting such documents, whether or not such information or data has been
submitted to the MHW.

9.5.   RESULTS OF JAPAN CLINICAL TRIALS: Prior to the Aksys Approval Date,
during the Term of this Agreement, Teijin will inform Aksys prior to beginning
any clinical trial which involves the use of the Products and provide Aksys with
a copy of the protocol to be used for each such trial. The results of such
trials, including information regarding adverse reactions or other problems
which may arise or be identified during the trial, will be reported to Aksys on
a timely basis. Teijin will comply with Aksys' reasonable requests for
additional information concerning such trials.

9.6.   USE OF DOCUMENTS, INFORMATION, AND DATA: Either party shall have the
right to refer to and use documents, information, and data received under this
Article 9 in the performance of its duties under Article 3 hereof and in
developing its applications for Approval; provided however that Aksys shall not
have the right to submit to the MHW any clinical or other experimental data
which Teijin has previously submitted to the MHW, unless such data were: (i)
developed by Aksys or (ii) obtained by Aksys from a third-party without breach
of this Agreement. Aksys shall in any case have the right to refer to and use
all documents, information, and data received under this Article 9 in developing
its submissions to the FDA and other regulatory agencies outside Japan.

9.7.   COST OF DOCUMENTS, INFORMATION, AND DATA: Article 4 hereof
notwithstanding, neither party shall be entitled to compensation from the other
party for documents, information, or data provided in accordance with this
Article 9.

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9.8.   LANGUAGE: All documents, information, and data provided by either party
in accordance with this Article 9 shall be provided in the language (e.g.
Japanese or English) in which such items were originally created, and neither
party shall be obligated to translate any item into another language.

                           ARTICLE 10: CONFIDENTIALITY

10.1.  CONFIDENTIAL INFORMATION: Aksys and Teijin acknowledge that, in the
course of performing their respective obligations under this Agreement, each
will receive information which is confidential and proprietary to the disclosing
party and which the disclosing party wishes to protect from public disclosure.
The term "Confidential Information" shall mean any information and data relating
to Technology or which shall be disclosed between the parties and marked
"Confidential" relating to their respective businesses, customers, products,
development results, marketing plans, financial status, intellectual property
rights, the terms of this Agreement, and technical information. In addition any
and all of the information, data and samples which Teijin or Aksys acquires
pursuant to Articles 3 and 9 hereof shall be considered Confidential
Information.

10.2.  RESTRICTIONS: Confidential Information shall remain the sole and
exclusive property of the disclosing party. The party receiving Confidential
Information shall use it only for the purpose of performing its obligations
under this Agreement, including its responsibilities under Article 3 and as
provided in Article 9 hereof, and shall not disclose or provide access to the
Confidential Information to any third party without the prior written consent of
the disclosing party except as required by applicable law. Each party shall
exercise the same degree of care to safeguard the confidentiality of the other
party's Confidential Information as it would exercise in protecting the
confidentiality of similar property of its own, and shall use its diligent
efforts to prevent inadvertent or unauthorized disclosure of all Confidential
Information. The foregoing shall not apply to information which a party can
show:

(i)    was already in the possession of such party prior to disclosure;

(ii)   has become publicly available without breach of this Agreement by such
       party;

(iii)  has been rightfully received by such party from a third party not under
       an obligation of confidence to the other party with respect thereto;

(iv)   was released for disclosure by the other party with its written consent;
       or,

(v)    was disclosed to the public pursuant to the requirement of a governmental
       agency or operation of law, provided that such party is obligated to use
       its best efforts to prevent or limit disclosure under such circumstances.

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10.3.  INJUNCTIVE RELIEF: The parties understand and agree that the disclosing
party will suffer immediate, irreparable harm in the event the receiving party
fails to comply with any of its obligations under this Article 10, that monetary
damages will be inadequate to compensate the disclosing party for such breach,
and that the disclosing party shall have the right to enforce this Article 10 by
injunctive or other equitable remedies. In the event that one party brings legal
action pursuant to this Article 10 and successfully obtains injunctive relief,
then the other party shall pay the attorneys' fees and other reasonable costs of
the party bringing such action. (The provisions of this Article 10.3 shall not
be limited in any way by the provisions of Articles 12 or 13.2 hereof.)

            ARTICLE 11: INFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS

11.1.  REPRESENTATIONS AND WARRANTIES: Neither Teijin nor Aksys is currently
aware of any third-party's intellectual property that would be infringed,
misappropriated, or otherwise violated by Version C as currently envisaged.

11.2   INDEMNIFICATION: Aksys hereby agrees to protect, defend, hold harmless
and indemnify Teijin from and against any and all claims, damages, liabilities,
losses and expenses arising out of any alleged or actual infringement of the
intellectual property of any third-party by Products sold by Aksys outside the
Territory. Teijin hereby agrees to protect, defend, hold harmless and indemnify
Aksys from and against any and all claims, damages, liabilities, losses and
expenses arising out of any alleged or actual infringement of the intellectual
property of any third-party by Products sold by Teijin in the Territory.

11.3.  INDEMNITY RESTRICTION: Notwithstanding Article 11.2 hereof, the
indemnifying party shall have no obligations for any claim under this Article 11
unless: (i) the indemnified party notifies the indemnifying party of such claim
as soon as practicable, but in no event less than fifteen (15) days after the
indemnified party receives notice thereof, (ii) the indemnified party tenders
control of the defense of such claim to the indemnifying party, and (iii) the
indemnified party provides the indemnifying party with all reasonable
cooperation in such defense of such claim. Furthermore, the indemnifying party
shall have no obligation for any claim under this Agreement if the Indemnified
Party makes any admission, settlement or other communication regarding such
claim without the prior written consent of the Indemnifying Party, which consent
shall not be unreasonably withheld. The indemnified party shall have the right
(but not the obligation) to participate in such defense or settlement, in which
event each party shall pay its respective attorneys' fees.

                       ARTICLE 12: LIMITATION OF LIABILITY

12.1.  DISCLAIMER OF WARRANTY: EXCEPT AS EXPRESSLY SET FORTH IN THIS AGREEMENT,
THE PARTIES MAKE NO REPRESENTATIONS AND EXTEND NO WARRANTIES OF ANY KIND, EITHER
EXPRESS OR IMPLIED, INCLUDING ANY

                                     - 13 -
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EXPRESS OR IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE. THE PARTIES EXPRESSLY DISCLAIM ANY REPRESENTATION, WARRANTY, COVENANT
OR CONDITION REGARDING THE COMPLETION OR FAILURE TO COMPLETE VERSION C.

12.2   INDEMNIFICATION BY AKSYS: Aksys shall indemnify and hold harmless Teijin,
its officers, agents, employees, and affiliates from any loss, claim, action,
damage, expense, or liability (including defense costs and attorneys' fees)
arising out of or related to: (i) any injury to Aksys' employees or agents while
at Teijin's facilities, (ii) the handling, use or sale by Aksys of any product
(including but not limited to any of the Products) which Aksys has purchased or
otherwise obtained from Teijin and (iii) the use in commerce of any product
(including but not limited to any of the Products) which Aksys has purchased or
otherwise obtained from Teijin.

12.3   INDEMNIFICATION BY TEIJIN: Teijin shall indemnify and hold harmless
Aksys, its officers, agents, employees, and affiliates from any loss, claim,
action, damage, expense, or liability (including defense costs and attorneys'
fees) arising out of or related to: (i) any injury to Teijin employees or agents
while at Aksys facilities, (ii) the handling, use or sale by Teijin of any
product (including but not limited to any of the Products) which Teijin has
purchased or otherwise obtained from Aksys and (iii) the use in commerce of any
product (including but not limited to any of the Products) which Teijin has
purchased or otherwise obtained from Aksys.

12.4.  EXCLUSION OF CONSEQUENTIAL DAMAGES: In no event shall either party be
liable or responsible to the other party for the loss of any actual or
anticipated profits, loss of time, inconvenience, commercial loss, or any other
damages arising from or related to either party's performance or failure to
perform under this Agreement.

                            ARTICLE 13: MISCELLANEOUS

13.1.  GOVERNING LAW: This Agreement shall be governed by, and construed in
accordance with, the laws of the State of Illinois, USA.

13.2.  ARBITRATION: The parties shall initially endeavor to resolve any disputes
by good-faith negotiations. If they are unable to resolve any differences
relating to or arising from this Agreement or alleged breach of this Agreement,
the matter(s) shall be submitted to arbitration in accordance with the
International Rules of the American Arbitration Association ("A.A.A.") then in
force. The number of arbitrators shall be three (3), with one (1) to be
appointed by each party and the third to be designated by the two
party-appointed arbitrators. Each party shall be responsible for their own costs
and expenses, including attorneys' fees, the fees for each party-appointed
arbitrator, disbursements, and filing fees. The place of arbitration shall be
Chicago, Illinois, USA. The decision of the arbitrators shall be final and
binding and the award may be entered in any court of competent jurisdiction.

                                     - 14 -
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13.3.  COUNTERPARTS: For convenience of the parties, this Agreement may be
executed in one or more counterparts, each of which shall be deemed an original
for all purposes, and all of which taken together shall constitute but one and
the same instrument.

13.4.  NOTICES: All notices, requests, demands, consents, waivers, approvals,
and other communications hereunder shall be in writing and shall be deemed to
have been duly given: (i) if delivered personally with receipt acknowledged,
(ii) if transmitted by telex, telefax, telegraph, or other like method (with
receipt acknowledged), or (iii) if mailed, postage prepaid, by certified mail,
return receipt requested, addressed as follows:

       IF TO TEIJIN:  Teijin Limited
                      Home Health Care Division
                      Tokyo Sakurada Bldg.
                      1-1-3, Nishi-Shimbashi
                      Minato-ku, Tokyo 105, Japan
                      Attn: General Manager, Planning Department
                      Telefax: 81-3-3506-4060

       IF TO AKSYS:   Aksys Limited
                      Two Marriott Drive
                      Lincolnshire, Illinois  60069, USA
                      Attn: Chief Executive Officer
                      Telefax: 1-847-229-2080

                      with a copy (which shall not constitute notice) to:

                      Aksys Japan, KK
                      2-28-1 Nihonbashi-Hamacho
                      Chuo-ku, Tokyo 103, Japan
                      Attn: President
                      Telefax: 81-3-3662-5040

or such other address as either party may designate for itself by written notice
given to the other party from time to time in the manner hereinabove provided.
Except as otherwise expressly provided herein, all communications hereunder
shall be deemed to be given, received, and dated on the date when delivered
personally, on the date of receipt of telex or telefax, or on the date of
delivery or refusal (if refused) of certified or registered mail.

13.5.  SEVERABILITY: In the event that any one or more of the provisions of this
Agreement is held invalid or unenforceable, such unenforceability shall not
affect any other provision, but this Agreement shall then be construed as if
such unenforceable provision or provisions had never been contained herein.

                                     - 15 -
<Page>

13.6.  HEADINGS: Headings and titles used herein are for convenience of
reference only and shall not control the construction or interpretation of any
provision hereof.

13.7.  INTEGRATION: This Agreement embodies the entire understanding and
agreement of the parties hereto with respect to the subject matter contained
herein, and supersedes all prior oral or written understandings and agreements
relating thereto except as expressly otherwise provided, and may not be altered,
modified, or waived in whole or in part, except in writing, signed by duly
authorized representatives of the parties.

13.8.  FORBEARANCE: The failure of either party to insist upon the performance
of any of the terms, covenants, conditions, or provisions of this Agreement
shall not be considered a waiver or relinquishment of continued compliance
therewith; nor shall a waiver by either party of any breach of any term,
covenant, condition, agreement, or provision constitute a waiver of any
subsequent breach of that term, covenant, condition, agreement or provision.

13.9.  ASSIGNMENT: The rights granted to and the obligations imposed upon the
parties under this Agreement shall not be assignable, or otherwise delegable,
transferable, or subject to encumbrance in any manner or degree to or in favor
of any person for any purpose by any act of either party or by operation of law
or otherwise, without the prior written consent of the other party, and any
attempt to assign, delegate, transfer, or encumber such rights or duties, in the
absence of the other party's prior written consent, shall be void and of no
force and effect; provided however that this Agreement may be assigned to any
third-party which has acquired all or substantially all of the business or
assets of either party to this Agreement. Notwithstanding the foregoing, this
Agreement shall be binding on any successors of the parties.

13.10. RELATIONSHIP: This Agreement supersedes and replaces the Joint
Development Agreement dated January 8, 1998 by and between Teijin and Aksys. The
parties acknowledge that this Agreement constitutes a fair and equitable basis
for their relationship. However in the event that during the term of this
Agreement the general situation and/or data upon which this Agreement is based
are substantially changed so that either party suffers severe and unforeseeable
hardship which it could not reasonably be expected to bear, the parties will
consult in good faith to find a solution acceptable to both parties. The parties
shall be independent contractors, and nothing herein shall be deemed to make
them partners, co-venturers or principal and agent.

13.11. AUDIT PROVISIONS: Aksys shall comply with Teijin's reasonable requests to
inspect Aksys' accounting records in order to determine Aksys' compliance with
Article 4.1 hereof. Teijin shall comply with Aksys' reasonable requests to
inspect Teijin's accounting records in order to determine Teijin's compliance
with Article 7 hereof. Either party may use a Certified Public Accountant or
other qualified third-party to perform on its behalf the inspections allowed
under this Article 13.11.

13.12. PUBLIC RELEASE: Except as required by law, neither party shall issue a
press release or make

                                     - 16 -
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any other public statement or disclosure regarding this Agreement, without the
prior written consent of the other party.

13.13. GOOD FAITH DISCUSSIONS: Aksys shall hold good-faith discussions with
Teijin before concluding any agreement with a third-party which would foreclose
to Teijin the possibility of marketing the Products in the Republic of China,
Korea, Taiwan, Singapore, Malaysia, Thailand, or Indonesia.

       IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed on the day and year first above written.

TEIJIN LIMITED                               AKSYS, LTD.

BY:      /s/ Toshimitsu Ishikawa             BY:      /s/ Lawrence H.N. Kinet
       -------------------------                    -------------------------
       Toshimitsu Ishikawa                          Lawrence H. N. Kinet
       Managing Director                            President
       General Manager                               and Chief Executive Officer
       Medical and Pharmaceutical Group

       Hereunto Duly Authorized                     Hereunto Duly Authorized

DATE:  June 21, 1999                         DATE:  June 16, 1999

                                     - 17 -<Page>

                                                                    Exhibit 10.5

                            STOCK PURCHASE AGREEMENT

       This Stock Purchase Agreement (this "Agreement") is made as of
January 7, 1998 (the "Effective Date") by and between Aksys, Ltd., a Delaware
corporation whose principal business office is at Two Marriott Drive,
Lincolnshire, Illinois 60069 (hereinafter called "Seller"),

                                       and

Teijin Limited, a Japanese corporation whose registered office is at 6-7,
Minami-honmachi 1-chome, Chuo-ku, Osaka 541, Japan (hereinafter called "Buyer").

                                   WITNESSETH:

       WHEREAS, Seller is engaged in the design and development of certain
healthcare products, especially hemodialysis products, in the United States of
America;

       WHEREAS, Buyer is engaged in the design, development, manufacture and
sale of certain healthcare medical products in Japan and is the major provider
of the home oxygen concentrators and services for patients in the Japanese
market;

       WHEREAS, Seller has been looking for an appropriate Japanese business
partner with respect to its hemodialysis products and Buyer is interested in
such products;

       WHEREAS, Seller and Buyer have been negotiating with respect to the joint
development of such products in Japan;

       WHEREAS, Seller has been seeking ways to expand its relationship with
Buyer and is willing to offer Buyer to make an equity investment in Seller;

       WHEREAS, Buyer is willing to make an equity investment in Seller in order
to establish and strengthen its relationship with Seller; and

       WHEREAS, Seller and Buyer now wish to set forth the terms and conditions
of the above-mentioned investment between the parties hereto.

       NOW, THEREFORE, the parties hereto have agreed as follows:

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                                    ARTICLE 1
                                   DEFINITIONS

       For purposes of this Agreement, the following terms have the meanings
specified or referred to in this Article 1:

       1.1    The term "Affiliate" shall have the meaning as such term is
defined in Rule 12b-2 under the Exchange Act.

       1.2    The term "Associate" shall have the meaning as such term is
defined in Rule 12b-2 under the Exchange Act.

       1.3    The term "Common Stock" shall mean the Common Stock, par value
U.S.$0.01 per share, of Seller.

       1.4    The term "Exchange Act" shall mean the Securities Exchange Act of
1934, as amended, or any successor law, and regulations and rules issued
pursuant to that Act or any successor law, all of which are effective in the
United States of America.

       1.5    The term "Joint Development Agreement" shall mean a Joint
Development Agreement, dated as of the date hereof, by and between the Parties.

       1.6    The term "Marketing Agreement" shall mean a Marketing Agreement to
be entered into by and among the Parties pursuant to the terms and conditions of
the Joint Development Agreement.

       1.7    The term "Parties" or "Party" shall collectively mean Seller and
Buyer or either of them individually.

       1.8    The term "Per Share Price" shall mean an amount equal to (i) the
average of the daily closing price for a share of Common Stock on the Nasdaq
Stock Market (National Market System) on each of the trading days during 90
consecutive calendar days immediately prior to the day which is 2 days before
the Effective Date MULTIPLIED BY (ii) 1.35.

       1.9    The term "Representatives of Buyer" shall mean: (i) Buyer's
directors, officers, employees, and advisors; and (ii) representatives of
Buyer's advisors.

       1.10   The term "Securities Act" shall mean the Securities Act of 1933,
as amended, or any successor law, and regulations and rules issued pursuant to
that Act or any successor law, all of which are effective in the United States
of America.

       1.11   The term "Shares" shall mean a number of shares of Common Stock
equal to (i) U.S. $5,000,000 DIVIDED BY (ii) the Per Share Price, rounded
upwards to the nearest integral

                                      - 2 -
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number of shares of Common Stock.

       1.12   The term "Subsidiary" shall mean any corporation with respect to
which a specified corporation (or a Subsidiary thereof) owns a majority of the
stock entitled to vote for the election of directors or which otherwise has the
power to vote or direct the voting of sufficient securities to elect a majority
of the directors.

                                    ARTICLE 2
                                     PURPOSE

       The purpose of this Agreement is to set forth terms and conditions of the
purchase by Buyer of Common Stock from Seller as a general framework for a
mutually beneficial cooperation between Seller and Buyer.

                                    ARTICLE 3
                           PURCHASE AND SALE OF SHARES

       3.1    BASIC TRANSACTION. On and subject to the terms and conditions of
this Agreement, Buyer agrees to purchase from Seller, and Seller agrees to sell
to Buyer, the Shares for the consideration specified below in this Article 3.

       3.2    PURCHASE PRICE. Buyer agrees to pay to Seller at the Closing U.S.
$5,000,000 (the "Purchase Price") by wire transfer of immediately available
funds.

       3.3    CLOSING. The closing of the transactions contemplated by this
Agreement (the "Closing") shall take place at the offices of Kirkland & Ellis in
Chicago, Illinois, commencing at 9:00 a.m., local time, on the third business
day following the satisfaction or waiver of all conditions to the obligations of
the Parties to consummate the transactions contemplated hereby (other than
conditions with respect to actions the respective Parties will take at the
Closing itself) or such other date as Buyer and Seller may mutually determine
(the "Closing Date").

       3.4    DELIVERY AT CLOSING. At the Closing, (i) Seller will deliver to
Buyer the certificate referred to in Section 8.1.3 below, (ii) Buyer will
deliver to Seller the certificate referred to in Section 8.2.3 below, (iii)
Seller will deliver to Buyer a stock certificate representing the Shares and
(iv) Buyer will deliver to Seller consideration specified in Section 3.2 above.

       3.5    LEGEND. The Shares are being issued pursuant to Section 4(2) of
the Securities Act. The certificate evidencing the Shares shall contain a
restrictive legend in substantially the following form:

              "The shares represented by this certificate have
              not been registered under the Securities Act of
              1933, as amended (the "Securities Act"), and such
              shares may

                                      - 3 -
<Page>

              not be sold or transferred unless the sale or
              transfer is in accordance with the registration
              requirements of the Securities Act, in conformity
              with the limitations of Rule 144 under the
              Securities Act or unless some other exemption from
              the registration requirements of the Securities Act
              is available with respect thereto."

                                    ARTICLE 4
                    REPRESENTATIONS AND WARRANTIES OF SELLER

       Seller represents and warrants to Buyer that the statements contained in
this Article 4 are correct and complete as of the date of this Agreement and
will be correct and complete as of the Closing Date (as though made then and as
though the Closing Date were substituted for the date of this Agreement
throughout this Article 4) with respect to itself.

       4.1    ORGANIZATION OF SELLER. Seller is duly organized, validly existing
and in good standing under the laws of State of Delaware.

       4.2    AUTHORIZATION OF TRANSACTION. Seller has full power and authority
(including full corporate power and authority) to execute and deliver this
Agreement and to perform its obligations hereunder. This Agreement constitutes
the valid and legally binding obligation of Seller, enforceable in accordance
with its terms and conditions. Seller need not give any notice to, make any
filing with, or obtain any authorization, consent or approval of any government
or governmental agency in order to consummate the transactions contemplated by
this Agreement. All of the Shares to be issued to Buyer have been duly
authorized and, upon issuance thereof, shall be validly issued, fully paid and
nonassessable. There are no preemptive rights or rights of subscription or
refusal with respect to the issuance of the Shares hereunder.

       4.3    NONCONTRAVENTION. Neither the execution and delivery of this
Agreement, nor the consummation of the transactions contemplated hereby, will
(a) violate any constitution, statute, regulation, rule, injunction, judgment,
order, decree, ruling, charge or other restriction of any government,
governmental agency or court to which Seller is subject or any provision of its
charter or bylaws or (b) conflict with, result in a breach of, constitute a
default under, result in the acceleration of, create in any party the right to
accelerate, terminate, modify or cancel, or require any notice under any
agreement, contract, lease, license, instrument or other arrangement to which
Seller is a party or by which it is bound or to which any of its assets is
subject.

       4.4    INTELLECTUAL PROPERTY. The patents and trademarks of Seller do
not, to the knowledge of the CEO of Seller as of the Effective Date, contravene,
conflict with, violate or infringe upon any patent or trademark of a third party
and no proprietary information or trade secret has been misappropriated by
Seller from any third party.

       4.5    SEC FILINGS. Seller has heretofore delivered to Buyer true,
correct and

                                      - 4 -
<Page>

complete copies of Seller's (i) Annual Report on Form 10-K for the year ended
December 31, 1996 and (ii) Quarterly Report on Form 10-Q for the quarter ended
September 30, 1997. As of their respective dates, the foregoing (including (x)
the financial information contained therein, (y) all exhibits and schedules
thereto and (z) documents incorporated by reference therein) did not contain any
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 light of
the circumstances under which they were made, not misleading.

       4.6    ABSENCE OF CERTAIN CHANGES OR EVENTS. Since September 30, 1997,
there has not been any material adverse change in the business, operations or
condition (financial or other) of Seller and its Subsidiaries, taken as a whole,
or any commitment by Seller or any of its Subsidiaries to any such change.

                                    ARTICLE 5
                               COVENANTS OF SELLER

       5.1    LISTING. Promptly following the issuance of the Shares, Seller
shall use its commercially best efforts to list the Shares on the Nasdaq Stock
Market (National Market System).

       5.2    SEC FILINGS. As long as Buyer holds any of the Shares issued
pursuant to this Agreement, Seller shall timely file with the Securities and
Exchange Commission all reports required to be filed by it pursuant to the
Exchange Act.

                                    ARTICLE 6
                     REPRESENTATIONS AND WARRANTIES OF BUYER

       Buyer represents and warrants to Seller that the statements contained in
this Article 6 are correct and complete as of the date of this Agreement and
will be correct and complete as of the Closing Date (as though made then and as
though the Closing Date were substituted for the date of this Agreement
throughout this Article 6) with respect to itself.

       6.1    ORGANIZATION OF BUYER. Buyer is a corporation duly organized,
validly existing, and in good standing under the laws of Japan.

       6.2    AUTHORIZATION OF TRANSACTION. Buyer has full power and authority
(including full corporate power and authority) to execute and deliver this
Agreement and to perform its obligations hereunder. This Agreement constitutes
the valid and legally binding obligation of Buyer, enforceable in accordance
with its terms and conditions. Buyer need not give any notice to, make any
filing with, or obtain any authorization, consent or approval of any government
or governmental agency in order to consummate the transactions contemplated by
this Agreement; PROVIDED, HOWEVER, that prior to the Closing Buyer is required
to submit a written notice with regard to the transactions contemplated by this
Agreement to the Minister of Finance of Japan (the "MOF") under the Foreign
Exchange and Trade Control Law of Japan, as amended.

                                      - 5 -
<Page>

       6.3    NONCONTRAVENTION Neither the execution and delivery of this
Agreement, nor the consummation of the transactions contemplated hereby, will
(a) violate any constitution, statute, regulation, rule, injunction, judgment,
order, decree, ruling, charge or other restriction of any government,
governmental agency or court to which Buyer is subject or any provision of its
articles of incorporation or regulations of board of directors or (b) conflict
with, result in a breach of, constitute a default under, result in the
acceleration of, create in any party the right to accelerate, terminate, modify
or cancel, or require any notice under any agreement, contract, lease, license,
instrument or other arrangement to which Buyer is a party or by which it is
bound or to which any of its assets is subject.

       6.4    INVESTMENT. Buyer understands that issuance of the Shares has not
been, and shall not be, registered under the Securities Act, or under any state
securities laws, and that the Shares are being offered and sold in reliance upon
United States federal and state exemptions for transactions not involving any
public offering. Buyer acknowledges that it is acquiring the Shares solely for
its own account for investment purposes, and not with a view to, or intention to
effect, the distribution thereof in violation of the Securities Act or any
applicable state securities laws, and that the Shares may not be disposed of in
contravention of the Securities Act or any applicable state securities laws.
Buyer represents that it is a sophisticated investor with knowledge and
experience in business and financial matters, is able to evaluate the risks and
benefits of the investment in the Shares, has received certain information
concerning Seller and has had the opportunity to obtain additional information
as desired in order to evaluate the merits of and the risks inherent in
purchasing the Shares. Buyer also represents that it is an "accredited investor"
as contemplated by Regulation D under the Securities Act.

       6.5    NO REGISTRATION UNDER JAPANESE SECURITIES LAW. Buyer understands
that the Shares have not been and will not be registered under the Securities
and Exchange Law of Japan, as amended, and represents that it has not offered or
sold, and agrees that it will not offer or sell, any Shares, directly or
indirectly in Japan or to or from any resident of Japan except in compliance
with applicable requirements of Japanese laws.

                                    ARTICLE 7
                               COVENANTS OF BUYER

       7.1    STANDSTILL. As a precondition to the execution of this Agreement
by Seller, Buyer agrees that until one year has elapsed since the later to occur
of either of (i) the expiration of the Joint Development Agreement or (ii) the
expiration of the Marketing Agreement, neither Buyer (including any person or
entity directly or indirectly, through one or more intermediaries, controlling
Buyer or controlled by Buyer or under common control with Buyer) nor any of the
Representatives of Buyer shall, nor shall Buyer permit any of its Associates or
Affiliates to, acting alone or as part of any group (a) in any manner acquire,
agree to acquire or make any proposal or offer to acquire, directly or
indirectly, any securities or property of Seller, (b) except at the specific
written request of Seller, propose to enter into, directly or indirectly, any
merger or business combination involving

                                      - 6 -
<Page>

Seller or to purchase, directly or indirectly, a material portion of the assets
of Seller, (c) make, or in any way participate, directly or indirectly, in any
"solicitation" of "proxies" or become a "participant" in any "election contest"
(as such terms are defined or used in the proxy rules of the Securities and
Exchange Commission) with respect to Seller, or otherwise seek to advise or
influence any person with respect to the voting of, any voting securities of
Seller, including by public announcement or written statement broadly
disseminated, (d) form, join or in any way participate in a "group" (within the
meaning of Section 13(d)(3) of the Exchange Act) with respect to any voting
securities of Seller, (e) otherwise act, alone or in concert with others, to
seek to control or influence the management, board of directors or policies or
affairs of Seller (PROVIDED that this subsection (e) shall not restrict the
right of Buyer to exercise any right granted to it under the Joint Development
Agreement or the Marketing Agreement), (f) disclose any intention, plan or
arrangement inconsistent with the foregoing or (g) advise, assist or encourage
any other persons in connection with any of the foregoing. Buyer also agrees
during such period not to request Seller (or its directors, officers, employees
or agents), directly or indirectly, to amend or waive any provision of this
Section 7.1 (including this sentence).

       7.2    SPECIFIC PERFORMANCE. Buyer agrees that, in the event of any
breach of the provisions of Section 7.1, Seller shall be entitled to equitable
relief, including injunction and specific performance, in addition to all other
remedies available to Seller at law or in equity.

       7.3    RIGHT OF BUYER TO ACQUIRE COMMON STOCK. Notwithstanding
Section 7.1 of this Agreement, Buyer (together with all of its Affiliates and
Associates and Representatives of Buyer) may acquire (by purchase of shares of
Common Stock on the Nasdaq Stock Market (National Market System) or otherwise)
up to but not more than ten percent of the Common Stock issued and outstanding
from time to time.

       7.4    RESALE RESTRICTION. Buyer agrees that it will not sell, transfer,
convey, assign, gift or otherwise dispose (a "Transfer") of the Shares to any
entity within one year from the Closing Date; PROVIDED that Buyer may Transfer
the Shares to any of its Affiliates (which Affiliates shall in turn be bound by
this Section 7.4). Any Transfer in violation of this Section 7.4 shall be null
and void, and need not be recognized by Seller or its transfer agent.

       7.5    JAPANESE FOREIGN EXCHANGE CONTROLS. Buyer shall take all action
and do all things necessary, proper or advisable in order to consummate and make
effective the transactions contemplated by this Agreement, including without
limitation promptly making any filing or report required under the Foreign
Exchange and Trade Control Law of Japan, as amended.

                                    ARTICLE 8
                        CONDITIONS TO OBLIGATION TO CLOSE

       8.1    CONDITIONS TO OBLIGATION OF BUYER. The obligation of Buyer to
consummate the transactions to be performed by it in connection with the Closing
is subject to satisfaction of the following conditions:

                                      - 7 -
<Page>

              8.1.1  the representations and warranties of Seller set forth in
    Article 4 above shall be true and correct in all material respects at and as
    of the Closing Date;

              8.1.2  no action, suit or proceeding shall be pending before any
    court or quasi-judicial or administrative agency of any federal, state,
    local or foreign jurisdiction, or before any arbitrator, wherein an
    unfavorable injunction, judgment, order, decree, ruling or charge would (a)
    prevent consummation of any of the transactions contemplated by this
    Agreement, (b) cause any of the transactions contemplated by this Agreement
    to be rescinded following consummation or (c) affect adversely the right of
    Buyer to own the Shares (and no such injunction, judgment, order, decree,
    ruling or charge shall be in effect);

              8.1.3  Seller shall have delivered to Buyer a certificate to the
    effect that each of the conditions specified above in Sections 8.1.1 and
    8.1.2 is satisfied in all respects, which certificate shall also state, as
    of a date within five days of the Closing Date, the number of issued and
    outstanding shares of Common Stock and the number of shares of Common Stock
    reserved for issuance;

              8.1.4  Buyer shall have submitted a written notice with regard to
    the transactions contemplated by this Agreement to the MOF under the Foreign
    Exchange and Trade Control Law of Japan, as amended, and the requisite
    waiting period (if any) thereunder shall have lapsed; and

              8.1.5  Buyer and Seller shall have entered into the Registration
    Rights Agreement in form and substance as set forth in Exhibit A attached
    hereto.

       Buyer may waive any condition specified in Section 8.1 if it executes a
writing so stating at or prior to the Closing.

       8.2    CONDITIONS TO OBLIGATIONS OF SELLER. The obligation of Seller to
consummate the transactions to be performed by it in connection with the Closing
is subject to satisfaction of the following conditions:

              8.2.1  the representations and warranties of Buyer set forth in
    Article 6 above shall be true and correct in all material respects at and as
    of the Closing Date;

              8.2.2  no action, suit or proceeding shall be pending before any
    court or quasi-judicial or administrative agency of any federal, state,
    local or foreign (including without limitation Japan) jurisdiction, or
    before any arbitrator, wherein an unfavorable injunction, judgement, order,
    decree, ruling or charge would (a) prevent consummation of any of the
    transactions contemplated by this Agreement or (b) cause any of the
    transactions contemplated by this Agreement to be rescinded following
    consummation (and no such injunction, judgment, order, decree, ruling or
    charge shall be in effect); and

                                      - 8 -
<Page>

              8.2.3 Buyer shall have delivered to Seller a certificate to the
    effect that each of the conditions specified above in Sections 8.2.1 and
    8.2.2 is satisfied in all respects.

       Seller may waive any condition specified in this Section 8.2 if it
executes a writing so stating at or prior to the Closing.

                                    ARTICLE 9
                                   TERMINATION

       9.1    TERMINATION OF AGREEMENT. A Party, as applicable, may terminate
this Agreement as provided below:

              9.1.1  Buyer and Seller may terminate this Agreement by mutual
    written consent at any time prior to the Closing;

              9.1.2  Buyer may terminate this Agreement by giving a written
    notice to Seller at any time prior to the Closing (a) in the event Seller
    has breached any material representation or warranty contained in this
    Agreement in any material respect, Buyer has notified Seller of the breach
    and the breach has continued without cure for a period of 30 days after the
    notice of such breach or (b) if the Closing shall not have occurred on or
    before February 28, 1998, by reason of the failure of any condition
    precedent under Section 8.1 hereof (unless the failure results primarily
    from Buyer itself breaching any representation or warranty contained in this
    Agreement); or

              9.1.3  Seller may terminate this Agreement by giving a written
    notice to Buyer at any time prior to the Closing (a) in the event Buyer has
    breached any material representation or warranty contained in this Agreement
    in any material respect, Seller has notified Buyer of the breach, and the
    breach has continued without cure for a period of 30 days after the notice
    of such breach or (b) if the Closing shall not have occurred on or before
    February 28, 1998, by reason of the failure of any condition precedent under
    Section 8.2 hereof (unless the failure results primarily from Seller itself
    breaching any representation or warranty contained in this Agreement).

       9.2    EFFECT OF TERMINATION. If either Party terminates this Agreement
pursuant to Section 9.1 above, all rights and obligations of the Parties
hereunder shall terminate without any liability of any Party to any other Party
(except for any liability of any Party then in breach).

                                      - 9 -
<Page>

                                   ARTICLE 10
                               GENERAL PROVISIONS

       10.1   EXPENSES. Except as otherwise expressly provided in this
Agreement, each Party will bear its respective expenses incurred in connection
with the preparation, execution and performance of this Agreement and the
contemplated transactions hereunder, including all fees and expenses of its
agents, representatives, legal counsel and accountants.

       10.2   PUBLIC ANNOUNCEMENT. Any public announcement or similar publicity
with respect to this Agreement or the contemplated transactions hereunder will
not be issued without the prior written consent of the other Party hereto,
except as required by law.

       10.3   NOTICES. All notices, consents, requests, demands and other
communications authorized or required to be given pursuant to this Agreement
shall be given in writing:

       If to Seller:     Aksys, Ltd.
                         Two Marriott Drive
                         Lincolnshire, IL 60069
                         United States of America
                         Attn: Chief Executive Officer
                         Telefax: 1-847-229-2080

       With a copy to:   Aksys Japan, KK
                         28-1, Nihonbashi-Hamacho 2-chome
                         Chuo-ku, Tokyo 103
                         Japan
                         Attn: President
                         Telefax: 81-3-3662-5040

       If to Buyer:      Teijin Limited
                         Home Health Care Division
                         Tokyo Sakurada Bldg.
                         1-3, Nishi-Shinbashi 1-chome
                         Minato-ku, Tokyo 105
                         Japan
                         Attn: General Manager, New Health Care Planning Dept.
                         Telefax: 81-3-3506-4060

       Notices under this Agreement shall be deemed effective on the earlier of:
actual receipt; one working day after dispatch when sent by telex, cable or by
telefax to the recipient's proper telex or telefax number, or when delivered by
hand, or ten working days after being sent by air mail, certified or registered
mail, postage pre-paid, return receipt requested, addressed as set out above (or
as otherwise designated by any Party in writing by notice given in accordance
with this paragraph).

                                     - 10 -
<Page>

       10.4   GOVERNING LAW. The provisions in this Agreement relating to the
Shares will be governed by the laws of the State of Illinois.

       10.5   ARBITRATION.

              10.5.1 DISPUTE RESOLUTION. All controversies, disputes or claims
    arising between the Parties in connection with, or with respect to, any
    provision of this Agreement which has not been resolved within 30 days after
    either of the Parties has notified the other Party in writing of such
    controversy, dispute or claim, shall be submitted for arbitration in
    accordance with the rules of the American Arbitration Association or any
    successor thereof. Arbitration shall take place in New York, New York.

              10.5.2 SELECTION OF ARBITRATORS. Each Party shall select one
    arbitrator (who shall not be counsel for such Party), and the two so
    designated shall select a third arbitrator. If either Party shall fail to
    designate an arbitrator within 14 days after arbitration is requested, or if
    the two arbitrators shall fail to select a third arbitrator within 21 days
    after arbitration is requested, then such arbitrator shall be selected by
    the American Arbitration Association or any successor thereto upon
    application of either Party. Judgment upon any award of the majority of
    arbitrators shall be binding and shall be entered in a court of competent
    jurisdiction. Subject to the provisions in this Agreement the award of the
    arbitrators may grant any relief which a court of general jurisdiction has
    the authority to grant, including, without limitation, award of damages
    and/or injunctive relief, and shall assess, in addition, the cost of the
    arbitration, including the reasonable fees of the arbitrators and reasonable
    attorneys' fees and costs of the prevailing Party, against the
    non-prevailing Party.

              10.5.3 ARBITRATION RULES. All disputes and claims shall be
    determined by arbitration in accordance with the Commercial Arbitration
    Rules of the American Arbitration Association (the "Rules") then in effect,
    except that such Rules shall be modified by this Agreement.

              10.5.4 ARBITRATION PROCEEDINGS. All arbitral proceedings arising
    under, or in connection with, this Agreement shall be governed by the
    Federal Rules of Civil Procedure of the United States. The arbitrators may
    shorten the periods of time otherwise applicable to the arbitral proceedings
    under such rules to permit the award to be made within the time limitation
    set forth in the previous sentence.

       10.6   ENTIRE AGREEMENT. This Agreement supersedes all prior agreements
between the Parties with respect to its subject matter and constitutes the
complete and exclusive statement of the agreement between the Parties with
respect to its subject matter. This Agreement may not be amended, waived or
modified except by an instrument in writing executed by the Parties.

       10.7   BINDING EFFECT. This Agreement shall be binding upon and shall
inure to the

                                     - 11 -
<Page>

benefit of the Parties and their successors and assigns; PROVIDED, HOWEVER, that
neither Party may assign any of its rights under this Agreement without prior
written consent of the other Party.

       10.8   SEVERABILITY. If any term, covenant, restriction or provision of
this Agreement is held invalid or unenforceable by any court of competent
jurisdiction, the remaining terms, covenants, restrictions and provisions of
this Agreement will remain in full force and effect, and shall in no way be
affected, impaired or invalidated; it being the intent of the Parties that they
would have executed the remaining terms, covenants, restrictions and provisions
without including any of such which may be hereafter declared invalid, void or
unenforceable.

                                     - 12 -
<Page>

       10.9   HEADINGS. The headings of Articles and Sections in this Agreement
are provided for convenience only and will not affect its construction or
interpretation.

                                     * * * *

                                     - 13 -
<Page>

       IN WITNESS WHEREOF, the Parties hereto have caused this Stock Purchase
Agreement to be executed by their duly authorized representatives as of the day
and year first above written.

                                 AKSYS, LTD.

                             By:   /s/ Lawrence H.N. Kinet
                                 --------------------------
                                 Lawrence H. N. Kinet
                                 Chairman & Chief Executive Officer

                                 TEIJIN LIMITED

                             By:   /s/ Masao Matsuzaki
                                 ---------------------
                                 Masao Matsuzaki
                                 Senior Managing Director and General Manager
                                 Medical & Pharmaceutical Group

                                     - 14 -

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