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                                                                    EXHIBIT 4.21

                          REGISTRATION RIGHTS AGREEMENT

         This REGISTRATION RIGHTS AGREEMENT (the "Agreement") is entered into as
of March 5, 2001, by and between ALTERRA HEALTHCARE CORPORATION, a Delaware
corporation (the "Company"), and the other parties listed on the signature page
hereto (collectively referred to as the "Investors" and each individually as an
"Investor").

                                    RECITALS:

         A. The Company has issued to the Investors Warrant Certificates dated
of even date herewith (the "Warrants") providing, among other things, for the
purchase by the Investors of the Company's Series B-1 Non-Voting Participating
Preferred Stock, stated value $75.00 per share (the "Series B-1 Stock").
Capitalized terms defined in the Warrants and not otherwise defined herein are
used herein with the same meanings as defined in the Warrants.

         B. The Company desires to grant to the Investors registration rights
with respect to the Series B-1 Stock (and certain other securities, including,
the Debentures (as hereinafter defined) and the Series B-1 Stock issuable
conversion thereof), and the Investors desires to receive such registration
rights, all in accordance with the terms of this Agreement.

         C. This Agreement is the Registration Rights Agreement referred to in
the Warrants.

         NOW, THEREFORE, in consideration of the premises and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties agree as follows:

         1. REGISTRABLE SECURITIES. For purposes of this Agreement, the term
"Registrable Securities" means each Series B-1 9.75% Convertible Pay-In-Kind
Debenture (collectively, the "Debentures") that may be issued by the Company
pursuant to the terms of that certain Loan Agreement dated as of March 5, 2001
between the Company and the Investors, each share of Series B-1 Stock into which
the Debentures are convertible, each share of Series B-1 Stock which may be
issued upon the exercise of the Warrants, each share of Common Stock into which
the shares of Series B-1 Stock may be converted at the option of the Company in
accordance with the designations thereof, and any Security issued with respect
to any of the foregoing upon any stock dividend, split or similar event, until,
in the case of such Registrable Securities, (i) it is effectively registered
under the Securities Act and disposed of in accordance with the registration
statement covering it; (ii) it is salable by the holder thereof pursuant to Rule
144(k) promulgated under the Securities Act; or (iii) it is sold to the public
pursuant to Rule 144 promulgated under the Securities Act, and, as a result of
an event or circumstance described in any of the foregoing clauses (i) through
(iii), the legends with respect to transfer restrictions required under the
Warrants (other than any such legends required solely as the consequences of the
fact that the Registrable Securities are owned by, or were previously owned by,
the Company or an Affiliate of the Company) are removed or removable in
accordance with the terms of the Warrants.



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         2. DEMAND REGISTRATIONS.

            2A. REQUEST FOR REGISTRATION.

               (i) At any time and from time to time after the date hereof, the
holders of at least 51% of the Registrable Securities then outstanding may
request registration under the Securities Act of all or any part of their
Registrable Securities (each, a "Demand Registration"), subject to the terms and
conditions of this Agreement. Any request (a "Registration Request") for the
Demand Registration shall specify (a) the approximate number of Registrable
Securities requested to be registered, and (b) the intended method of
distribution of such securities.

               (ii) Subject to subsection (i) above and paragraph 4, the holders
of Registrable Securities will be entitled to request up to two (2) Demand
Registrations at any time and from time to time as provided herein.

               (iii) A registration will not count as one of the Demand
Registrations paid for by the Company (as provided in paragraph 5B) unless the
holders of the Registrable Securities are able to register and sell at least 50%
of the Registrable Securities requested to be included in such registration.

               (iv) The Company will not include in any Demand Registration any
Securities other than shares of (a) Securities (the "Senior Registrable
Securities") for which the holders thereof have registration rights under and
pursuant to that certain Registration Rights Agreement dated as of May 31, 2000
among the Company and the other parties thereto, as amended (the "Senior
Registration Rights Agreement"), (b) Registrable Securities and (c) Securities
to be registered for offering and sale on behalf of the Company without the
prior written consent of the holders of a majority of the shares of Registrable
Securities initially requesting registration. If the managing underwriter(s), if
any, of the offering to be effected pursuant to a Demand Registration advise the
Company in writing that in their opinion the number of shares of Senior
Registrable Securities, Registrable Securities and, if permitted hereunder,
other Securities in such offering, exceeds the number of Senior Registrable
Securities, Registrable Securities and other Securities, if any, which can be
sold in an orderly manner in such offering within a price range acceptable to
the holders of a majority of the Registrable Securities initially requesting
registration, the Company will include in such registration, (x) first, and
prior to the inclusion of any Registrable Securities and other Securities which
are not Senior Registrable Securities, the number of Senior Registrable
Securities requested to be included pursuant to the Senior Registration Rights
Agreement which in the opinion of such underwriters can be sold in an orderly
manner within the price range of such offering, pro rata among the respective
holders thereof on the basis of the number of Senior Registrable Securities that
each such holder has requested the Company to include in such registration, and
(y) second, and prior to the inclusion of any Securities which are not
Registrable Securities, the number of Registrable Securities requested to be
included pursuant to paragraphs 2A(i) and 3A which in the opinion of such
underwriters can be sold in an orderly manner within the price range of such
offering, pro rata among the respective holders thereof on the basis of the
number of Registrable Securities that each such holder has requested the Company
to include in such registration.


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            2B. SELECTION OF UNDERWRITER. The holders of a majority of the then
outstanding Registrable Securities proposed to be registered will have the right
to select the managing underwriter or underwriters to manage the offering,
subject to the Company's approval, which will not be unreasonably withheld,
provided that the managing underwriter or underwriters shall be the firm or
firms that managed the Company's most recently completed underwritten public
offering of Common Stock unless the holders of a majority of the then
outstanding Registrable Securities proposed to be registered shall object to
such firm or firms for reasons related to the ability of such firm or firms to
effectively manage the offering and the Company may consent to the selection of
such other managing underwriter or underwriters in such event.

         3. PIGGYBACK REGISTRATIONS.

            3A. RIGHT TO PIGGYBACK. If the Company proposes to register any of
its Securities under the Securities Act (other than registration solely in
connection with an employee benefit or stock ownership plan or the resale of the
Company's convertible debentures issued prior to the date of this Agreement or a
registration relating solely to a transaction to which Rule 145 (as promulgated
under the Securities Act) applies) and the registration form to be used may be
used for the registration of Registrable Securities (a "Piggyback
Registration"), the Company will give prompt written notice to all holders of
Registrable Securities of its intention to effect such a registration (each a
"Piggyback Notice"). Subject to subparagraphs 3B and 3C below, the Company will
include in such registration all shares of Registrable Securities which holders
of Registrable Securities request the Company to include in such registration by
written notice given to the Company within fifteen (15) days after the date of
sending of the Company's notice, subject to the terms and provisions of this
paragraph 3.

            3B. PRIORITY ON PRIMARY REGISTRATIONS. If a Piggyback Registration
relates to an underwritten public offering of equity Securities by the Company
and the managing underwriters advise the Company in writing that in their
opinion the number of Securities requested to be included in such registration
exceeds the number which can be sold in an orderly manner in such offering
within a price range acceptable to the Company, then the Company will include in
such registration (i) first, the Securities proposed to be sold by the Company;
(ii) second, the Senior Registrable Securities requested to be included in such
registration pursuant to the Senior Registration Rights Agreement pro rata among
the holders of such Senior Registrable Securities on the basis of the Senior
Registrable Securities owned by each holder thereof; and (iii) third, the
Registrable Securities requested to be included in such registration pro rata
among the holders of such Registrable Securities on the basis of the Registrable
Securities owned by each such holder.

            3C. PRIORITY ON SECONDARY REGISTRATIONS. If a Piggyback Registration
relates to an underwritten public offering of equity Securities by holders of
the Company's Securities and the managing underwriters advise the Company in
writing that in their opinion the number of Securities requested to be included
in such registration exceeds the number which can be sold in an orderly manner
in such offering within a price range acceptable to the holders initially
requesting such registration, the Company will include in such registration (i)
first, the Senior Registrable Securities requested to be included in such
registration pursuant to the Senior Registration Rights Agreement pro rata among
the holders of such Senior Registrable Securities



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on the basis of the Senior Registrable Securities owned by each holder thereof;
(ii) second, the Registrable Securities requested to be included in such
registration pro rata among the holders of such Registrable Securities on the
basis of the number of the Registrable Securities owned by each such holder; and
(iii) third, Securities other than Senior Registrable Securities and Registrable
Securities.

         4. REGISTRATION PROCEDURES. Whenever the holders of Registrable
Securities have requested that any Registrable Securities be registered pursuant
to this Agreement, the Company will use its best efforts to effect the
registration and the sale of such Registrable Securities in accordance with the
intended method of distribution thereof and will as expeditiously as possible:

               (i) prepare and file with the Securities and Exchange Commission
a registration statement with respect to such Registrable Securities and use its
best efforts to cause such registration statement to become effective; provided,
that before filing a registration statement or prospectus or any amendments or
supplements thereto, the Company will furnish to the counsel selected by the
holders of a majority of the Registrable Securities covered by such registration
statement copies of all such documents proposed to be filed, which documents
will be subject to the review of such counsel;

               (ii) prepare and file with the Securities and Exchange Commission
such amendments and supplements to such registration statement and the
prospectus used in connection therewith as may be necessary to keep such
registration statement effective for a period of not less than one hundred
twenty days (120) in the event of an offering to be made pursuant to Rule 415
under the Securities Act (or such lesser time as necessary to permit the holders
to complete the distribution described in such registration statement), and
comply with the provisions of the Securities Act with respect to the disposition
of all Securities covered by such registration statement during such period in
accordance with the intended methods of distribution by the sellers thereof set
forth in such registration statement;

               (iii) furnish to each seller of Registrable Securities such
number of copies of such registration statement, each amendment and supplement
thereto, the prospectus included in such registration statement (including each
preliminary prospectus) and such other documents as such seller may reasonably
request in order to facilitate the disposition of the Registrable Securities
owned by such seller;

               (iv) use its best efforts to register or qualify such Registrable
Securities under the securities or blue sky laws of such jurisdictions as any
seller reasonably requests and do any and all other acts and things which may be
reasonably necessary or advisable to enable such seller to consummate the
disposition in such jurisdictions of the Registrable Securities owned by such
seller, provided, that the Company will not be required (i) to qualify generally
to do business in any jurisdiction where it would not otherwise be required to
qualify but for this subparagraph, (ii) to subject itself to taxation in any
such jurisdiction or (iii) to consent to general service of process in any such
jurisdiction;

               (v) notify each seller of such Registrable Securities, at any
time when a prospectus relating thereto is required to be delivered under the
Securities Act, of the


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happening of any event as a result of which the prospectus included in such
registration statement contains an untrue statement of a material fact or omits
any fact necessary to make the statements therein not misleading, and, at the
request of any such seller, the Company will prepare a supplement or amendment
to such prospectus so that, as thereafter delivered to the Investors of such
Registrable Securities, such prospectus will not contain an untrue statement of
a material fact or omit to state any fact necessary to make the statements
therein not misleading; provided, however, the Company shall not be obligated to
prepare and furnish any such prospectus supplements or amendments relating to
any material nonpublic information during any time period not to exceed one
hundred twenty (120) days (such time period, the "Black-Out Period") during
which the Board of Directors of the Company has determined that, for good
business reasons, the disclosure of such material nonpublic information during
such Black-Out Period is contrary to the best interests of the Company in the
circumstances and is not otherwise required under applicable law (including
applicable securities laws), in which event the Company shall advise each holder
of Registerable Securities covered by such registration statement that such
prospectus requires updating and, accordingly, should not be used pending
further amendment, and promptly following the expiration of such Black-Out
Period, the Company shall comply with the provisions of this paragraph 4(v).

               (vi) cause all such Registrable Securities to be listed on each
securities exchange on which similar Securities issued by the Company are then
listed and to be qualified for trading on each system on which similar
Securities issued by the Company are from time to time qualified;

               (vii) provide a transfer agent and registrar for all such
Registrable Securities not later than the effective date of such registration
statement and thereafter maintain such a transfer agent and registrar;

               (viii) enter into such customary agreements (including
underwriting agreements in customary form) and take all such other actions as
the holders of a majority of the shares of Registrable Securities being sold or
the underwriters, if any, reasonably request in order to expedite or facilitate
the disposition of such Registrable Securities;

               (ix) make available for inspection by any underwriter
participating in any disposition pursuant to such registration statement and any
attorney, accountant or other agent retained by any such underwriter, all
financial and other records, pertinent corporate documents and properties of the
Company, and cause the Company's officers, directors, employees and independent
accountants to supply all information reasonably requested by any such
underwriter, attorney, accountant or agent in connection with such registration
statement;

               (x) otherwise use its best efforts to comply with all applicable
rules and regulations of the Securities and Exchange Commission, and make
available to its security holders, as soon as reasonably practicable, an
earnings statement covering the period of at least twelve (12) months beginning
with the first day of the Company's first full calendar quarter after the
effective date of the registration statement, which earnings statement shall
satisfy the provisions of Section 11(a) of the Securities Act and Rule 158
thereunder;


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               (xi) permit any holder of Registrable Securities which might be
deemed, in the sole and exclusive judgment of such holder, to be an underwriter
or a controlling person of the Company, to participate in the preparation of
such registration or comparable statement and to require the insertion therein
of material, furnished to the Company in writing, which in the reasonable
judgment of such holder and its counsel should be included;

               (xii) in the event of the issuance of any stop order suspending
the effectiveness of a registration statement, or of any order suspending or
preventing the use of any related prospectus or suspending the qualification of
any Registrable Securities included in such registration statement for sale in
any jurisdiction, the Company will use its reasonable best efforts promptly to
obtain the withdrawal of such order; and

               (xiii) furnish to each Investor a copy, or upon request, a signed
counterpart, addressed to such Investor (and the underwriters, if any) of (a) an
opinion of counsel for the Company, dated the effective date of such
registration statement (or, if such registration includes an underwritten public
offering, dated the date of closing under the underwriting agreement), and (b) a
"comfort" letter, dated the effective date of such registration statement (or,
if such registration includes an underwritten public offering, dated the date of
the closing under the underwriting agreement), signed by the independent public
accountants who have audited the Company's financial statements included in such
registration statement, covering substantially the same matters with respect to
such registration statement (and the prospectus included therein) and, in the
case of the accountants' letter, with respect to events subsequent to the date
of such financial statements, as are customarily covered in opinions of issuer's
counsel and in accountants letters delivered to the underwriters in underwritten
public offerings of securities and such other matters as such seller may
reasonably request.

         If any such registration or comparable statement refers to any holder
by name or otherwise as holder of any Securities of the Company and if, in its
sole and exclusive judgment, such holder is or might be deemed to be a
controlling person of the Company, such holder shall have the right to require
(a) the inclusion in such registration statement of language, in form and
substance satisfactory to such holder, to the effect that the holding of such
Securities by such holder is not to be construed as a recommendation by such
holder of the investment quality of the Company's Securities covered thereby and
that such holding does not imply that such holder will assist in meeting any
future financial requirements of the Company, or (b) in the event that such
reference to such holder by name or otherwise is not required by the Securities
Act or any similar federal statute then in force, the deletion of the reference
to such holder; provided, that with respect to this clause (b), such holder
shall furnish to the Company an opinion of counsel to such effect, which opinion
and counsel shall be reasonably satisfactory to the Company.

         Notwithstanding anything herein to the contrary, the Company shall not
be required to effect a Demand Registration (i) within ninety (90) days
preceding the anticipated effective date of a public offering of the Common
Stock that has been approved by the Board of Directors at the time of the
Registration Request; (ii) within one hundred twenty (120) days of any
registration of the Common Stock under the Securities Act in which the holders
of the Registrable Securities had a right to participate pursuant to this
Agreement; or (iii) if the Board of Directors reasonably determines in good
faith that filing a registration statement would require the Company to disclose
material nonpublic information, which if disclosed would be contrary to


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the best interests of the Company for good business reasons, and which is not
required by law to be disclosed, provided that the Company may only delay the
filing of a registration statement pursuant to this clause (iii) once per
calendar year for a period not to exceed one hundred twenty (120) days.

         5. REGISTRATION EXPENSES.

            5A. DEFINITION. The term "Registration Expenses" means all expenses
incident to the Company's performance of or compliance with this Agreement,
including, without limitation, all registration and filing fees, fees and
expenses of compliance with securities or blue sky laws, printing, messenger and
delivery expenses, and fees and expenses of counsel for the Company and all
independent certified public accountants, underwriters (excluding underwriting
discounts and commissions, which shall be paid by the selling stockholders out
of the proceeds of the offering) and other Persons retained by the Company.

            5B. PAYMENT. The Company shall pay the Registration Expenses in
connection with two (2) Demand Registrations and any and all Piggyback
Registrations. In connection with each Demand Registration and each Piggyback
Registration, the Company will reimburse the holders of Registrable Securities
covered by such registration for the reasonable fees and disbursements of one
counsel chosen by the holders of a majority of the Registrable Securities
initially requesting such registration.

         6. INDEMNIFICATION.

            6A. INDEMNIFICATION BY THE COMPANY. The Company agrees to indemnify,
to the extent permitted by law, each holder of Registrable Securities, its
officers and directors and each Person who controls such holder (within the
meaning of the Securities Act) against all losses, claims, damages, liabilities
and expenses caused by any untrue or alleged untrue statement of material fact
contained in any registration statement, prospectus or preliminary prospectus or
any amendment thereof or supplement thereto, or any omission or alleged omission
of a material fact required to be stated therein or necessary to make the
statements therein not misleading, except insofar as the same are caused by or
contained in any information furnished in writing to the Company by such holder
expressly for use therein or by such holder's failure to deliver a copy of the
registration statement or prospectus or any amendments or supplements thereto
after the Company has furnished such holder with a sufficient number of copies
of the same; provided, that the obligations of the Company hereunder shall not
apply to amounts paid in settlement of any such losses, claims, damages,
liabilities or expenses (or actions in respect thereof) if such settlement is
effected without the consent of the Company (which consent shall not be
unreasonably withheld). In connection with an underwritten offering, the Company
will indemnify such underwriters, their officers and directors and each Person
who controls such underwriters (within the meaning of the Securities Act) to the
same extent as provided above with respect to the indemnification of the holders
of Registrable Securities unless otherwise provided in the underwriting
agreement.

            6B. INDEMNIFICATION BY HOLDERS. In connection with any registration
statement in which a holder of Registrable Securities is participating, each
such holder will furnish to the Company in writing such information and
affidavits as the Company reasonably



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requests for use in connection with any such registration statement or
prospectus and, to the extent permitted by law, will indemnify the Company, its
directors and officers and each Person who controls the Company (within the
meaning of the Securities Act) against any losses, claims, damages, liabilities
and expenses resulting from any untrue or alleged untrue statement of material
fact contained in the registration statement, prospectus or preliminary
prospectus or any amendment thereof or supplement thereto or any omission or
alleged omission of a material fact required to be stated therein or necessary
to make the statements therein not misleading, but only to the extent that such
untrue statement or omission is contained in any information or affidavit so
furnished in writing by such holder and stated to be specifically for use
therein; provided, that (i) the obligation to indemnify will be individual to
each holder and will be limited to the net amount of proceeds received by such
holder from the sale of Registrable Securities pursuant to such registration
statement and (ii) the obligations of such holder hereunder shall not apply to
amounts paid in settlement of any such losses, claims, damages, liabilities or
expenses (or actions in respect thereof) if such settlement is effected without
the consent of such holder (which consent shall not be unreasonably withheld).

            6C. NOTICE; DEFENSE OF CLAIMS. Any Person entitled to
indemnification hereunder will (i) give prompt written notice to the
indemnifying party of any claim with respect to which it seeks indemnification
and (ii) unless in such indemnified party's reasonable judgment a conflict of
interest between such indemnified and indemnifying parties may exist with
respect to such claim, permit such indemnifying party to assume the defense of
such claim with counsel reasonably satisfactory to the indemnified party. If
such defense is assumed, the indemnifying party will not be subject to any
liability for any settlement made by the indemnified party without its consent
(but such consent will not be unreasonably withheld). An indemnifying party who
is not entitled to, or elects not to, assume the defense of a claim will not be
obligated to pay the fees and expenses of more than one counsel for all parties
indemnified by such indemnifying party with respect to such claim, unless in the
reasonable judgment of any indemnified party a conflict of interest may exist
between such indemnified party and any other of such indemnified parties with
respect to such claim.

            6D. CONTRIBUTION. If the indemnification provided for in this part 6
is held by a court of competent jurisdiction to be unavailable to an indemnified
party with respect to any loss, liability, claim, damage or expense referred to
herein, then the indemnifying party, in lieu of indemnifying such indemnified
party hereunder, shall contribute to the amount paid or payable by such
indemnified party as a result of such loss, liability, claim, damage, or expense
in such proportion as is appropriate to reflect the relative fault of the
indemnifying party, on the one hand, and of the indemnified party, on the other,
in connection with the statements or omissions that resulted in such loss,
liability, claim, damage, or expense, as well as any other relevant equitable
considerations. The relative fault of the indemnifying party and of the
indemnified party shall be determined by reference to, among other things,
whether the untrue or alleged untrue statement of a material fact or the
omission to state a material fact relates to information supplied by the
indemnifying party or by the indemnified party and the parties' relative intent,
knowledge, access to information, and opportunity to correct or prevent such
statement or omission. The obligation to contribute will be individual to each
holder of Registrable Securities and will be limited to the amount by which the
net amount of proceeds received by such holder from the sale of Registrable
Securities exceeds the amount of losses, liabilities, damages, and



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expenses which such holder has otherwise been required to pay by reason of such
statements or omissions.

            6E. SURVIVAL. The indemnification and contribution provided for
under this Agreement will remain in full force and effect regardless of any
investigation made by or on behalf of the indemnified party or any officer,
director or controlling Person of such indemnified party and will survive the
transfer of Securities.

         7. PARTICIPATION IN UNDERWRITTEN REGISTRATIONS. No Person may
participate in any registration hereunder which is underwritten unless such
Person (i) agrees to sell such Person's Securities on the basis provided in any
underwriting arrangements approved by the Person or Persons entitled hereunder
to approve such arrangements, and (ii) completes and executes all
questionnaires, powers of attorney, indemnities, underwriting agreements and
other documents required under the terms of such underwriting arrangements;
provided, that no holder of Registrable Securities included in any underwritten
registration shall be required to make any representations or warranties to the
Company or the underwriters other than representations and warranties regarding
such holder as are required by the underwriters.

         8. MISCELLANEOUS.

            8A. NO INCONSISTENT AGREEMENTS. The Company will not hereafter enter
into any agreement with respect to its Securities which is inconsistent with or
violates the rights granted to the holders of Registrable Securities in this
Agreement.

            8B. ADJUSTMENTS AFFECTING REGISTRABLE SECURITIES. The Company will
not take any action, or permit any change to occur, with respect to its
Securities for the purpose of materially and adversely affecting the ability of
the holders of Registrable Securities to include such Registrable Securities in
a registration undertaken pursuant to this Agreement or materially and adversely
affecting the marketability of such Registrable Securities in any such
registration (including, without limitation, effecting a stock split or a
combination of shares); provided, that this paragraph 8B shall not apply to
actions or changes with respect to the Company's business, earnings or revenues
where the effect of such actions or changes on the Registrable Securities is
merely incidental.

            8C. NOTICES. All notices, requests, consents, and other
communications under this Agreement shall be in writing and shall be delivered
personally or by facsimile transmission or by overnight delivery service or 72
hours after having been mailed by first class certified or registered mail,
return receipt requested, postage prepaid:

         If to the Company, at Alterra Healthcare Corporation, 10000 Innovation
Drive, Milwaukee, Wisconsin 53226, Attention: Chief Executive Officer, (fax:
(414) 918-5055), or at such other address or addresses as may have been
furnished in writing by the Company to the Investors, with a copy (which shall
not constitute notice) to Rogers & Hardin LLP, 2700 International Tower, 229
Peachtree Street, NE, Atlanta, Georgia 30303, Attention: Alan C. Leet, Esq. (fax
(404) 525-2224).

         If to an Investor, at its address set forth in the Purchase Agreement,
or at such other address or addresses as may have been furnished to the Company
in writing by such Investor.


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         Notices provided in accordance with this paragraph 8C shall be deemed
delivered upon personal delivery or two (2) business days after deposit in the
mail.

            8D. REMEDIES. Any Person having rights under any provision of this
Agreement will be entitled to enforce such rights specifically to recover
damages caused by reason of any breach of any provision of this Agreement and to
exercise all other rights granted by law. The parties hereto agree and
acknowledge that money damages may not be an adequate remedy for any breach of
the provisions of this Agreement and that any party may in its sole discretion
apply to any court of law or equity of competent jurisdiction (without posting
any bond or other security) for specific performance and for other injunctive
relief in order to enforce or prevent violation of the provisions of this
Agreement.

            8E. AMENDMENTS AND WAIVERS; REFERENCES TO SPECIFIED PERCENTAGE OR
MAJORITY OF REGISTRABLE SECURITIES. Except as otherwise provided herein, no
waiver, amendment, modification, termination or cancellation of this Agreement,
or of any of the terms or conditions hereof, shall be effective unless made in
writing signed by the Company and the holders of 66-2/3% of the then outstanding
Registrable Securities; provided, however, that no such waiver, amendment,
modification, termination or cancellation to the definition of "Registrable
Securities" or the priorities granted to the holders of the Registrable
Securities in paragraph 2A(iv), 3B or 3C shall be effective unless made in
writing signed by the holders of a majority of the then outstanding Registrable
Securities. All references in this Agreement either to a specified percentage
(e.g., 51%, 66 2/3%) or a "majority" of certain Registrable Securities shall be
determined based upon the original aggregate purchase price of such Registrable
Securities.

            8F. SUCCESSORS AND ASSIGNS. This Agreement, and the rights and
obligations of each Investor hereunder, may be assigned by such Investor to any
person or entity to which shares of Registrable Securities are transferred by
such Investor, and such transferee shall be deemed an "Investor" for purposes of
this Agreement; provided, that the transferee provides written notice of such
assignment to the Company.

            8G. SEVERABILITY. The invalidity or unenforceability of any
provision of this Agreement shall not affect the validity or enforceability of
any other provision of this Agreement.

            8H. ENTIRE AGREEMENT. This Agreement, together with the Warrants,
embodies the entire agreement and understanding between the parties hereto with
respect to the subject matter hereof and supersedes all prior agreements and
understandings relating to such subject matter.

            8I. HEADINGS. The headings of this Agreement are for convenience
only and do not constitute a part of this Agreement.

            8J. GOVERNING LAW. The construction, validity and interpretation of
this Agreement will be governed by the internal laws of the State of Delaware,
without giving effect to any choice of law or conflict of law provision or rule
(whether of the State of Delaware or any


                                       10

<PAGE>   11


other jurisdiction) that would cause the application of the laws of any
jurisdiction other than the State of Delaware.

            8K. FURTHER ASSURANCES. Each party to this Agreement hereby
covenants and agrees, without the necessity of any further consideration, to
execute and deliver any and all such further documents and take any and all such
other actions as may be necessary to appropriate to carry out the intent and
purposes of this Agreement and to consummate the transactions contemplated
hereby.

            8L. COUNTERPARTS. This Agreement may be executed and delivered
(including delivery by facsimile) in one or more counterparts, each of which
shall be deemed to be an original, but all of which shall be one and the same
document.

            8N. RULE 144 REPORTING. With a view to making available the benefits
of certain rules and regulations of the Securities and Exchange Commission that
may permit sale of the Registrable Securities to the public without
registration, the Company agrees to use its reasonable efforts to:

               (i) Make and keep public information regarding the Company
available as those terms are understood and defined in Rule 144 under the
Securities Act, at all times from and after ninety (90) days following the
effective date of the first registration under the Securities Act filed by the
Company for an offering of its Securities to the general public;

               (ii) File with the Securities and Exchange Commission in a timely
manner all reports and other documents required of the Company under the
Securities Act and the Exchange Act at any time after it has become subject to
such reporting requirements.

               (iii) So long as a holder owns any Registrable Securities,
furnish to the holder forthwith upon written request a written statement by the
Company as to its compliance with the reporting requirements of Rule 144 (at any
time from and after ninety (90) days following the effective date of the first
registration statement filed by the Company for an offering of its Securities to
the general public), and of the Securities Act and the Exchange Act (at any time
after it has become subject to such reporting requirements), a copy of the most
recent annual or quarterly report of the Company, and such other reports and
documents so filed as a holder of Registrable Securities may reasonably request
in availing itself of any rule or regulation of the Securities and Exchange
Commission allowing a holder of Registrable Securities to sell any such
Securities without registration.

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         IN WITNESS WHEREOF, this Registration Rights Agreement has been
executed by the parties hereto through their respective duly authorized officers
or representatives as of the date first written above.

                              COMPANY:

                              ALTERRA HEALTHCARE CORPORATION



                              By:       /s/ Kristin A. Ferge
                                 ----------------------------------------------
                                 Name:  Kristin A. Ferge
                                 Title: Vice President and Assistant Secretary

                        INVESTORS:

                        RDVEPCO, L.L.C.
                                 By: RDV Altco, L.L.C., a member
                                 By: RDV Corporation, a member

                                 By:    /s/ Robert H. Schierbeek
                                 ----------------------------------------------
                                 Name:  Robert H. Schierbeek
                                 Title: Treasurer

                        THE TORONTO DOMINION BANK

                                 By:    /s/ Rick Greene
                                 ----------------------------------------------
                                 Name:  Rick Greene
                                 Title: ASO

                        HOLIDAY RETIREMENT 2000, LLC

                                 By:    /s/ Norman L. Brenden
                                 ----------------------------------------------
                                 Name:  Norman L. Brenden
                                 Title: Chief Financial Officer

                        HBK MASTER FUND L.P.
                                 By: HBK Investments L.P., its investment
                                     manager


                                 By:    /s/ William E. Rose
                                 ----------------------------------------------
                                 Name:  William E. Rose
                                 Title: