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                                                                     EXHIBIT 4.3
                          AMENDMENT TO RIGHTS AGREEMENT

         This Amendment (the "Amendment") is made as of the 26th day of April,
2000, to the Rights Agreement dated as of December 10, 1998 (the "Rights
Agreement') between ALTERRA HEALTHCARE CORPORATION, a Delaware corporation
formerly known as Alternative Living Services, Inc. (the "Company"), and
AMERICAN STOCK TRANSFER & TRUST COMPANY, as Rights Agent (the "Rights Agent").

                                   WITNESSETH:

         WHEREAS, the Board of Directors of the Company on December 10, 1998,
authorized the issuance of certain rights to purchase Common Stock of the
Company and declared a dividend of such rights; and

         WHEREAS, as of December 10, 1998, the Company and the Rights Agent
entered into the Rights Agreement to set forth their mutual agreements with
respect to the rights authorized by the Board of Directors on December 10, 1998;
and

         WHEREAS, the Board of Directors of the Company on April 25, 2000
authorized an amendment to the terms of the Rights Agreement;

         NOW, THEREFORE, in consideration of the premises and the mutual
agreements herein set forth, the parties hereby agree as follows:

         1.       All terms used in this Amendment which are not defined in this
                  Amendment have the meaning given those terms in the Agreement.

         2.       Section 1(a) of the Rights Agreement is hereby amended and
                  restated in its entirety as follows:

                           (a)      "Acquiring Person" shall mean any Person (as
                                    such term is hereinafter defined) who or
                                    which, together with all Affiliates and
                                    Associates (as such terms are hereinafter
                                    defined) of such Person, shall be the
                                    Beneficial Owner (as such term is
                                    hereinafter defined) of 15% or more of the
                                    Common Shares of the Company then
                                    outstanding, but shall not include (i) the
                                    Company, (ii) any Subsidiary (as such term
                                    is hereinafter defined) of the Company,
                                    (iii) any employee benefit plan of the
                                    Company or any Subsidiary of the Company,
                                    (iv) any entity holding Common Shares for or
                                    pursuant to the terms of any such plan or
                                    (v) any Exempt Person. Notwithstanding the
                                    foregoing, no Person shall become an
                                    "Acquiring Person" as the result of an
                                    acquisition of Common Shares by the Company
                                    which, by reducing the number of shares
                                    outstanding, increases the proportionate
                                    number of shares beneficially owned by such
                                    Person to 15% or more of the Common Shares
                                    of the Company then outstanding; provided,
                                    however, that if a Person shall become the
                                    Beneficial Owner of 15% or more of
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                                    the Common Shares of the Company then
                                    outstanding by reason of share purchases by
                                    the Company and shall, after such share
                                    purchases by the Company, become the
                                    Beneficial Owner of any additional Common
                                    Shares of the Company, then such Person
                                    shall be deemed to be an "Acquiring Person".
                                    Notwithstanding the foregoing, if the Board
                                    of Directors of the Company determines in
                                    good faith that a Person who would otherwise
                                    be an "Acquiring Person", as defined
                                    pursuant to the foregoing provisions of this
                                    paragraph (a), has become such
                                    inadvertently, and such Person divests as
                                    promptly as practicable a sufficient number
                                    of Common Shares so that such Person would
                                    no longer be an "Acquiring Person", as
                                    defined pursuant to the foregoing provisions
                                    of this paragraph (a), then such Person
                                    shall not be deemed to be an "Acquiring
                                    Person" for any purposes of this Agreement.

         3.       Section 1 of the Rights Agreement is hereby amended by adding
                  a new Section 1(g)-1 to read in its entirety as follows:

                           "(g)-1 "Exempt Person" shall mean (i) each Purchaser
                           (as defined in that certain Purchase Agreement (the
                           "Purchase Agreement") dated as of April 26, 2000 (the
                           "Purchase Date") by and among the Company and each
                           such Purchaser referenced therein, including any
                           permitted assignee of any Purchaser (each a "First
                           Tier Owner" and, collectively, the "First Tier
                           Owners"); (ii) the Affiliates and Associates of each
                           such First Tier Owner; and (iii) any Person not
                           covered by (ii), above, who or which is the
                           Beneficial Owner of Common Shares beneficially owned
                           by a First Tier Owner solely by reason of the
                           relationship of such Person to such First Tier Owner
                           or to any Affiliate or Associate of such First Tier
                           Owner (each Person described in this clause (iii), a
                           "Second Tier Owner"); provided, however, any such (x)
                           First Tier Owner, (y) Affiliate and Associate of each
                           such First Tier Owner, and (z) Second Tier Owner
                           (each such Person described in the foregoing clauses
                           (x), (y) and (z), a "Subject Owner") shall cease to
                           be an Exempt Person at the time that such Subject
                           Owner is the Beneficial Owner of a percentage of the
                           outstanding Common Shares of the Company that is more
                           than the sum of (A) the lowest percentage of the
                           outstanding Common Shares of the Company beneficially
                           owned by such Subject Owner at the close of business
                           on the Purchase Date (including for purposes thereof
                           the Common Shares that may be beneficially owned by
                           such Subject Owner, upon or after such date,
                           resulting from (1) the purchase or the exercise of
                           any exchange, conversion, put or similar right or
                           feature (including, without limitation, the right to
                           receive securities in the form of dividends or
                           interest), of (a) the securities to be purchased by
                           any First Tier Owner or for which any such First Tier
                           Owner has an option to purchase pursuant to the
                           Purchase Agreement (the "Purchased Securities") or
                           (b) the securities so issued or issuable pursuant to
                           such rights or features (the "Derivative Securities")
                           or the payment of any
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                           interest or dividends in respect of the Purchased
                           Securities or Derivative Securities and (2) all First
                           Tier Owners being deemed a "group" within the meaning
                           of Rule 13d-5 under the Exchange Act solely as a
                           result of their acquisition of Purchased Securities
                           pursuant to the Purchase Agreement) or at any time
                           thereafter, (B) any increase in such percentage
                           referred to in the foregoing clause (A) caused solely
                           by the acquisition of Common Shares by the Company,
                           and (C) 1%.

         4.       This Amendment shall be deemed to be a contract made under the
                  laws of the State of Delaware and for all purposes shall be
                  governed by and construed in accordance with the laws of such
                  state applicable to contracts to be made and performed
                  entirely within such state.

         5.       The Amendment may be executed in any number of counterparts
                  and each of such counterparts shall for all purposes be deemed
                  to be an original, and all such counterparts shall together
                  constitute but one and the same instrument.

         6.       If any term, provision, covenant or restriction of this
                  Amendment is held by a court of competent jurisdiction or
                  other authority to be invalid, illegal, or unenforceable, the
                  remainder of the terms, provisions, covenants and restrictions
                  of this First Amendment shall remain in full force and effect
                  and shall in no way be affected, impaired or invalidated.

         7.       Except as specifically set forth in this Amendment, the Rights
                  Agreement shall remain in full force and effect.



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         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed and their respective corporate seals to be hereunto affixed and
attested, all as of the day and year first above written.

                                    ALTERRA HEALTHCARE CORPORATION



                                    By: /s/ William F. Lasky
                                        ----------------------------------------
                                            Name: William F. Lasky
                                                  ------------------------------
                                            Title: President & CEO
                                                   -----------------------------
         Attest:

         /s/ Mark W. Ohlendorf
         ----------------------------
         ----------------------------

                     AMERICAN STOCK TRANSFER & TRUST COMPANY



                                    By: /s/ Herbert J. Lemmer
                                        ----------------------------------------
                                            Name: Herbert J. Lemmer
                                                  ------------------------------
                                            Title: Vice President
                                                   -----------------------------
         Attest:

         /s/ Susan Silber
         ----------------------------
         ----------------------------