EXHIBIT B

                          REGISTRATION RIGHTS AGREEMENT

            This  Registration  Rights Agreement (this  "AGREEMENT") is made and
entered  into as of April 4, 2005, by and among  Calypte Biomedical Corporation,
a Delaware corporation (the "COMPANY"), and the investors signatory hereto (each
a "INVESTOR" and collectively, the "INVESTORS").

            This Agreement is made pursuant to the Purchase Agreement,  dated as
of  April 4,  2005,  among  the  Company  and  the  Investors  (the  "PURCHASE
AGREEMENT").

            The Company and the Investors hereby agree as follows:

      1.  Definitions.  Capitalized  terms used and not otherwise defined herein
that are defined in the Purchase  Agreement  shall have the meanings  given such
terms in the Purchase Agreement. As used in this Agreement,  the following terms
shall have the respective meanings set forth in this Section 1:

            "EFFECTIVE  DATE"  means  the date that the  Registration  Statement
filed pursuant to Section 2(a) is first declared effective by the Commission.

            "EFFECTIVENESS  DATE"  means (a) with  respect  to the  Registration
Statement  required to be filed under Section  2(a),  the earlier of: (a)(i) the
120th day following  the Closing Date,  and (ii) the fifth Trading Day following
the date on which the  Company  is  notified  by the  Commission  that the First
Registration  Statement  will not be reviewed or is no longer subject to further
review  and  comments  and  (b)  with  respect  to any  additional  Registration
Statements that may be required pursuant to Section 2(b), the earlier of (i) the
120th day following (x) if such  Registration  Statement is required because the
Commission  shall have notified the Company in writing that certain  Registrable
Securities  were not eligible for inclusion on a previously  filed  Registration
Statement,  the date or time on which the Commission shall indicate as being the
first date or time that such  Registrable  Securities  may then be included in a
Registration  Statement, or (y) if such Registration Statement is required for a
reason other than as described in (x) above, the date on which the Company first
knows,  or  reasonably  should have  known,  that such  additional  Registration
Statement(s)  is required,  and (ii) the fifth Trading Day following the date on
which  the  Company  is  notified  by  the  Commission   that  such   additional
Registration  Statement  will not be reviewed or is no longer subject to further
review and comment.

            "EFFECTIVENESS  PERIOD"  shall have the meaning set forth in Section
2(a).

            "EXCHANGE  ACT"  means  the  Securities  Exchange  Act of  1934,  as
amended.

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            "FILING  DATE" means (a) with  respect to the  initial  Registration
Statement  required to be filed under Section  2(a),  the 45th day following the
Closing Date and (b) with respect to any additional Registration Statements that
may be required  pursuant to Section  2(b),  the 45th day  following (x) if such
Registration  Statement is required  because the Commission  shall have notified
the Company in writing that certain Registrable Securities were not eligible for
inclusion  on a previously  filed  Registration  Statement,  the date or time on
which the  Commission  shall  indicate as being the first date or time that such
Registrable Securities may then be included in a Registration  Statement, or (y)
if such Registration  Statement is required for a reason other than as described
in (x) above,  the date on which the Company first knows,  or reasonably  should
have known, that such additional Registration Statement(s) is required.

            "HOLDER" or "HOLDERS"  means the holder or holders,  as the case may
be, from time to time of Registrable Securities.

            "INDEMNIFIED  PARTY"  shall  have the  meaning  set forth in Section
5(c).

            "INDEMNIFYING  PARTY"  shall have the  meaning  set forth in Section
5(c).

            "LOSSES" shall have the meaning set forth in Section 5(a).

            "NOTES" means, collectively,  each of the promissory notes issued or
issuable under the Purchase Agreement.

            "PROCEEDING"  means  an  action,   claim,  suit,   investigation  or
proceeding   (including,   without  limitation,   an  investigation  or  partial
proceeding, such as a deposition), whether commenced or threatened.

            "PROSPECTUS"  means  the  prospectus   included  in  a  Registration
Statement  (including,  without  limitation,  a  prospectus  that  includes  any
information  previously  omitted from a prospectus filed as part of an effective
registration  statement  in  reliance  upon  Rule  430A  promulgated  under  the
Securities Act), as amended or supplemented by any prospectus  supplement,  with
respect  to  the  terms  of  the  offering  of any  portion  of the  Registrable
Securities  covered by a Registration  Statement,  and all other  amendments and
supplements to the  Prospectus,  including  post-effective  amendments,  and all
material  incorporated by reference or deemed to be incorporated by reference in
such Prospectus.

            "REGISTRABLE  SECURITIES"  means the (a) Underlying  Shares issuable
upon  conversion of the Notes  (assuming  such Notes are held until the maturity
date thereof and all interest is accreted to principal  thereunder together with
any  securities  issued or  issuable  upon any stock  split,  dividend  or other
distribution,  recapitalization  or  similar  event,  or  any  conversion  price
adjustment with respect  thereto),  (b) Warrant Shares issuable upon exercise of
the Warrants,  (c) Anti-Dilution  Entitlements (as defined in the Amendment) and
(d) New Entitlements (as defined in the Amendment).

            "REGISTRATION  STATEMENT" means the initial  registration  statement
required  to be  filed  in  accordance  with  Section  2(a)  and any  additional
registration  statement, if any, contemplated by Section 2(b), and including, in
each case, the Prospectus,  amendments and supplements to each such registration
statement or  Prospectus,  including  pre- and  post-effective  amendments,  all
exhibits  thereto,  and all material  incorporated  by reference or deemed to be
incorporated by reference in such registration statement.

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            "RULE 144" means Rule 144 promulgated by the Commission  pursuant to
the  Securities  Act,  as such Rule may be  amended  from  time to time,  or any
similar  rule  or  regulation   hereafter   adopted  by  the  Commission  having
substantially the same effect as such Rule.

            "RULE 415" means Rule 415 promulgated by the Commission  pursuant to
the  Securities  Act,  as such Rule may be  amended  from  time to time,  or any
similar  rule  or  regulation   hereafter   adopted  by  the  Commission  having
substantially the same effect as such Rule.

            "RULE 424" means Rule 424 promulgated by the Commission  pursuant to
the  Securities  Act,  as such Rule may be  amended  from  time to time,  or any
similar  rule  or  regulation   hereafter   adopted  by  the  Commission  having
substantially the same effect as such Rule.

            "SECURITIES ACT" means the Securities Act of 1933, as amended.

      2. Registration.

            (a) On or prior to each Filing Date,  the Company  shall prepare and
file with the  Commission a  Registration  Statement  covering the resale of all
Registrable  Securities  not  already  covered  by  an  existing  and  effective
Registration Statement for an offering to be made on a continuous basis pursuant
to Rule  415.  The  Registration  Statement  shall  be on Form  SB-2 or Form S-3
(except  if the  Company  is not  then  eligible  to  register  for  resale  the
Registrable Securities on Form SB-2 or Form S-3, in which case such registration
shall be on another appropriate form for such purpose) and shall contain (except
if otherwise  required pursuant to written comments received from the Commission
upon a  review  of such  Registration  Statement)  the  "Plan  of  Distribution"
attached hereto as Annex A. The Company shall cause each Registration  Statement
to be declared  effective  under the  Securities Act as soon as possible but, in
any event, no later than its Effectiveness  Date, and shall use its best efforts
to keep each Registration  Statement continuously effective under the Securities
Act until the second  year  after the date that the  Registration  Statement  is
declared  effective by the Commission or such earlier date when all  Registrable
Securities  covered by the Registration  Statement have been sold or may be sold
without volume restrictions pursuant to Rule 144(k) as determined by the counsel
to the Company  pursuant to a written  opinion letter to such effect,  addressed
and  acceptable to the Company's  transfer  agent and the affected  Holders (the
"EFFECTIVENESS  PERIOD").  The initial  Registration  Statement  shall include a
number of Registrable Securities equal to the sum of (a) 31,312,382,  the number
of Underlying  Shares  issuable upon an assumed  conversion in full of the Notes
(assuming  for such  purpose  that the Notes  are held  until  their  respective
scheduled  Maturity  Dates and all interest  accretes to principal  for the life
thereof), (b) 38,666,667, the number of shares issuable upon exercise in full of
the Warrants,  (c) 7,936,001,  the number of shares  issuable in connection with
the Anti-Dilution Entitlements and (d) 396,802, the number of shares issuable in
connection with the New Entitlements.

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            (b) If (i) for any reason the Commission  does not permit all of the
Registrable  Securities  to be  included  in the  Registration  Statement  filed
pursuant to Section 2(a) or for any other reason all such Registrable Securities
are not then  included in an effective  Registration  Statement or (ii) from and
after the date of the Stockholder  Approval upon such terms as the anti-dilution
provisions of the Notes would alter the Conversion Price, thereby resulting in a
greater number of Registrable  Securities being issuable to the Investors,  then
the Company shall  prepare and file as soon as possible  after the date on which
the  Commission  shall indicate as being the first date or time that such filing
may be made,  but in any  event  by the  Filing  Date  therefor,  an  additional
Registration  Statement  covering the resale of all  Registrable  Securities not
already  covered by an existing  and  effective  Registration  Statement  for an
offering to be made on a continuous  basis pursuant to Rule 415, on Form SB-2 or
Form S-3 (except if the Company is not then  eligible to register for resale the
Registrable Securities on Form SB-2 or Form S-3, in which case such registration
shall be on another  appropriate form for such purpose).  Each such Registration
Statement  shall  contain  (except if  otherwise  required  pursuant  to written
comments  received  from  the  Commission  upon a  review  of such  Registration
Statement) the "Plan of  Distribution"  attached  hereto as Annex A. The Company
shall cause each such Registration  Statement to be declared effective under the
Securities  Act as soon as  possible  but,  in any  event,  no  later  than  its
Effective  Date,  and  shall  use its best  efforts  to keep  such  Registration
Statement  continuously  effective  under the  Securities  Act during the entire
Effectiveness Period.

            (c) If: (i) a Registration Statement is not filed on or prior to its
Filing Date (if the Company files a Registration Statement without affording the
Holders the opportunity to review and comment on the same as required by Section
3(a) hereof, the Company shall not be deemed to have satisfied this clause (i)),
or (ii) a Registration  Statement is not declared effective by the Commission on
or prior to its required  Effectiveness Date, or (iii) after its Effective Date,
without regard for the reason thereunder or efforts therefore, such Registration
Statement  ceases for any reason to be effective and available to the Holders as
to all Registrable Securities to which it is required to cover at any time prior
to the expiration of its  Effectiveness  Period for more than an aggregate of 20
Trading Days for any twelve month period in the Effectiveness Period (which need
not be consecutive) (any such failure or breach being referred to as an "EVENT,"
and for purposes of clauses (i) or (ii) the date on which such Event occurs,  or
for  purposes  of clause  (iii) the date  which  such 20  Trading  Day period is
exceeded,  being  referred  to as "EVENT  DATE"),  then in addition to any other
rights the Holders may have under the Transaction  Documents or under applicable
law or at equity:  (x) on the Event Date the Company shall pay to each Holder an
amount, as partial liquidated damages and not as a penalty, equal to 1.0% of the
aggregate amount of principal  outstanding  under the Notes held by such Holder,
such  payment  being  either in cash or (but only if the Equity  Conditions  Are
Satisfied)  in Common Stock at a per share price equal to 80% of the VWAP of the
Common Stock for the ten Trading Days  preceding  the date on which such payment

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is due, provided, that in the event the Company fails to deliver such registered
shares of Common Stock by the 10th Trading Day following  such Event Date,  such
payment  shall  be,  at the  discretion  of the  Holder,  in all  cash;  and (y)
beginning with the one (1) month anniversary following each such Event Date, and
on each monthly  anniversary  thereafter (if the applicable Event shall not have
been cured by such date) until the applicable  Event is cured, the Company shall
pay to each  Holder  an  amount,  as  partial  liquidated  damages  and not as a
penalty,  equal to 2.0% of the aggregate amount of principal  outstanding  under
the Notes held by such Holder, such payment being either in cash or (but only if
the Equity  Conditions Are Satisfied) in Common Stock at a per share price equal
to 80% of the VWAP of the Common  Stock for the ten Trading Days  preceding  the
date on which such payment is due, provided, that in the event the Company fails
to  deliver  such  registered  shares of Common  Stock by the 10th  Trading  Day
following the monthly  anniversary  of each such Event Date,  such payment shall
be, at the  discretion  of the Holder,  in all cash.  The parties agree that the
Company will not be liable for liquidated  damages under this Section in respect
of the Warrants.  Notwithstanding anything to the contrary contained herein, the
Company will not be liable for liquidated damages under this Section 2(c) in the
event that any  Underlying  Shares  issuable  upon  conversion of the Notes that
constitute   interest   accreted  to  principal   thereunder,   Warrant  Shares,
Anti-Dilution  Entitlements or New Entitlements that are included in the initial
Registration  Statement  filed  pursuant to Section 2(a) herein are not declared
effective on or prior to the Effectiveness  Date applicable to such Registration
Statement  solely due to the Commission not permitting  such  Underlying  Shares
issuable  upon  conversion  of the Notes that  constitute  interest  accreted to
principal  thereunder,   Warrant  Shares,   Anti-Dilution  Entitlements  or  New
Entitlements  to be  included  in the  initial  Registration  Statement.  If the
Company fails to pay any partial  liquidated damages pursuant to this Section in
full within  seven days after the date  payable,  the Company  will pay interest
thereon  at a rate of 18% per  annum  (or such  lesser  maximum  amount  that is
permitted to be paid by applicable  law) to the Holder,  accruing daily from the
date such partial liquidated  damages are due until such amounts,  plus all such
interest thereon,  are paid in full. The partial  liquidated damages pursuant to
the terms  hereof  shall  apply on a daily  pro-rata  basis for any portion of a
month  prior to the cure of an Event,  including  in the case of the first Event
Date.

            (d) Each  Holder  agrees  to  furnish  to the  Company  a  completed
Questionnaire  in the form  attached  to this  Agreement  as Annex B (a "SELLING
HOLDER  QUESTIONNAIRE").  The  Company  shall not be  required  to  include  the
Registrable  Securities of a Holder in a Registration Statement and shall not be
required to pay any liquidated or other damages under Section 2(c) to any Holder
who  fails  to  furnish  to  the  Company  a  fully  completed   Selling  Holder
Questionnaire at least two Trading Days prior to the Filing Date (subject to the
requirements set forth in Section 3(a)).

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      3. Registration Procedures.

            In connection with the Company's registration obligations hereunder,
the Company shall:

            (a) Not less  than  three  Trading  Days  prior to the  filing  of a
Registration  Statement or any related Prospectus or any amendment or supplement
thereto,  the  Company  shall  furnish  to each  Holder  copies of the  "Selling
Stockholders" section of such document,  the "Plan of Distribution" and any risk
factor contained in such document that addresses  specifically  this transaction
or the Selling  Stockholders,  as proposed to be filed which  documents  will be
subject to the review of such Holder.  The Company shall not file a Registration
Statement,  any Prospectus or any amendments or supplements thereto in which the
"Selling  Stockholder" section thereof differs from the disclosure received from
a Holder in its Selling Holder Questionnaire (as amended or supplemented).

            (b) (i)  Prepare  and file  with  the  Commission  such  amendments,
including  post-effective  amendments,  to each  Registration  Statement and the
Prospectus  used in  connection  therewith  as may be  necessary  to  keep  such
Registration  Statement  continuously effective as to the applicable Registrable
Securities for its Effectiveness Period and prepare and file with the Commission
such  additional  Registration  Statements in order to register for resale under
the Securities  Act all of the  Registrable  Securities;  (ii) cause the related
Prospectus to be amended or supplemented by any required Prospectus  supplement,
and as so  supplemented  or  amended  to be filed  pursuant  to Rule 424;  (iii)
respond as promptly as  reasonably  possible to any comments  received  from the
Commission with respect to each Registration  Statement or any amendment thereto
and, as promptly as  reasonably  possible  provide the Holders true and complete
copies  of all  correspondence  from  and to the  Commission  relating  to  such
Registration Statement that would not result in the disclosure to the Holders of
material and non-public  information  concerning the Company; and (iv) comply in
all material respects with the provisions of the Securities Act and the Exchange
Act with  respect to the  Registration  Statements  and the  disposition  of all
Registrable Securities covered by each Registration Statement.

            (c) Notify the Holders as promptly as reasonably  possible  (and, in
the case of (i)(A) below, not less than three Trading Days prior to such filing)
and (if  requested by any such  Person)  confirm such notice in writing no later
than  one  Trading  Day  following  the  day  (i)(A)  when a  Prospectus  or any
Prospectus supplement or post-effective amendment to a Registration Statement is
proposed to be filed; (B) when the Commission notifies the Company whether there
will be a "review" of such  Registration  Statement and whenever the  Commission
comments in writing on such  Registration  Statement  (the Company shall provide
true and complete copies of any such comments and all written  responses thereto
to each Holder that pertains to such Holder as a Selling  Shareholder  or to the
Plan of  Distribution,  but not  information  which the Company  believes  would
constitute  material and non-public  information);  and (C) with respect to each
Registration Statement or any post-effective amendment, when the same has become
effective;  (ii) of any request by the  Commission or any other Federal or state
governmental authority for amendments or supplements to a Registration Statement

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or  Prospectus  or for  additional  information;  (iii) of the  issuance  by the
Commission of any stop order  suspending  the  effectiveness  of a  Registration
Statement covering any or all of the Registrable Securities or the initiation of
any  Proceedings  for that  purpose;  (iv) of the  receipt by the Company of any
notification  with respect to the suspension of the  qualification  or exemption
from  qualification  of  any of  the  Registrable  Securities  for  sale  in any
jurisdiction,  or the  initiation  or  threatening  of any  Proceeding  for such
purpose;  and (v) of the  occurrence  of any event or passage of time that makes
the financial  statements  included in a Registration  Statement  ineligible for
inclusion  therein  or any  statement  made in such  Registration  Statement  or
Prospectus or any document  incorporated or deemed to be incorporated therein by
reference  untrue in any material respect or that requires any revisions to such
Registration  Statement,  Prospectus or other  documents so that, in the case of
such Registration  Statement or the Prospectus,  as the case may be, it will not
contain any untrue  statement  of a material  fact or omit to state any material
fact required to be stated therein or necessary to make the statements  therein,
in light of the circumstances under which they were made, not misleading.

            (d) Use its reasonable best efforts to avoid the issuance of, or, if
issued, obtain the withdrawal of (i) any order suspending the effectiveness of a
Registration  Statement,  or  (ii)  any  suspension  of  the  qualification  (or
exemption from  qualification) of any of the Registrable  Securities for sale in
any jurisdiction, at the earliest practicable moment.

            (e) Furnish to each Holder,  without charge,  at least one conformed
copy of each Registration  Statement and each amendment thereto and all exhibits
to the extent requested by such Person (excluding those previously  furnished or
incorporated by reference)  promptly after the filing of such documents with the
Commission.

            (f)  Upon   notification  by  the  Commission  that  a  Registration
Statement  will not be  reviewed or is no longer  subject to further  review and
comments,  the Company shall request acceleration of such Registration Statement
such  that it  becomes  effective  at 5:00  p.m.  (New  York  City  time) on the
Effective Date.

            (g) Deliver to each Holder, by 9:00 a.m. (New York City time) on the
day  following  the  Effective  Date,  without  charge,  as many  copies of each
Prospectus  or  Prospectuses  (including  each  form  of  prospectus)  and  each
amendment or  supplement  thereto as such Persons may  reasonably  request.  The
Company  hereby  consents to the use of such  Prospectus  and each  amendment or
supplement  thereto  by each of the  selling  Holders  in  connection  with  the
offering and sale of the Registrable  Securities  covered by such Prospectus and
any amendment or supplement thereto.

            (h) Prior to any public offering of Registrable Securities,  use its
best  efforts to register or qualify or  cooperate  with the selling  Holders in
connection  with the  registration  or  qualification  (or  exemption  from such
registration or qualification) of such Registrable Securities for offer and sale
under the  securities  or Blue Sky laws of all  jurisdictions  within the United
States, to keep each such registration or qualification (or exemption therefrom)
effective  during the  Effectiveness  Period and to do any and all other acts or
things necessary or advisable to enable the disposition in such jurisdictions of
the Registrable  Securities  covered by the Registration  Statements;  provided,
that the Company  shall not be required to qualify  generally  to do business in
any jurisdiction where it is not then so qualified or subject the Company to any
material tax in any such jurisdiction where it is not then so subject.

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            (i) Cooperate with the Holders to facilitate the timely  preparation
and delivery of certificates representing Registrable Securities to be delivered
to a transferee  pursuant to the  Registration  Statements,  which  certificates
shall be  free,  to the  extent  permitted  by the  Purchase  Agreement,  of all
restrictive  legends,  and to enable such  Registrable  Securities to be in such
denominations and registered in such names as any such Holders may request.

            (j)  Upon  the  occurrence  of any  event  contemplated  by  Section
3(c)(v), as promptly as reasonably possible,  prepare a supplement or amendment,
including a post-effective amendment, to the affected Registration Statements or
a supplement to the related Prospectus or any document incorporated or deemed to
be incorporated  therein by reference,  and file any other required  document so
that, as thereafter delivered, no Registration Statement nor any Prospectus will
contain an untrue  statement of a material fact or omit to state a material fact
required to be stated  therein or necessary to make the statements  therein,  in
light of the circumstances under which they were made, not misleading.

      4.  Registration   Expenses.   All  fees  and  expenses  incident  to  the
performance  of or compliance  with this Agreement by the Company shall be borne
by the Company whether or not any Registrable  Securities are sold pursuant to a
Registration  Statement.  The fees and  expenses  referred  to in the  foregoing
sentence shall include, without limitation, (i) all registration and filing fees
(including,  without  limitation,  fees and expenses (A) with respect to filings
required  to be made with any Trading  Market on which the Common  Stock is then
listed for trading,  and (B) in compliance with applicable  state  securities or
Blue Sky laws), (ii) printing expenses (including, without limitation,  expenses
of printing certificates for Registrable Securities and of printing prospectuses
if the  printing of  prospectuses  is  reasonably  requested by the holders of a
majority of the Registrable Securities included in the Registration  Statement),
(iii) messenger, telephone and delivery expenses, (iv) fees and disbursements of
counsel for the Company, (v) Securities Act liability insurance,  if the Company
so desires  such  insurance,  and (vi) fees and  expenses  of all other  Persons
retained by the Company in connection with the  consummation of the transactions
contemplated  by this Agreement.  In addition,  the Company shall be responsible
for all of its internal expenses incurred in connection with the consummation of
the transactions contemplated by this Agreement (including,  without limitation,
all salaries and expenses of its  officers  and  employees  performing  legal or
accounting  duties),  the expense of any annual  audit and the fees and expenses
incurred in  connection  with the listing of the  Registrable  Securities on any
securities exchange as required hereunder.

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      5. Indemnification.

            (a)   Indemnification   by   the   Company.   The   Company   shall,
notwithstanding  any termination of this Agreement,  indemnify and hold harmless
each Holder, the officers,  directors,  agents,  investment advisors,  partners,
members,  shareholders  and employees of each of them,  each Person who controls
any such  Holder  (within  the  meaning of Section 15 of the  Securities  Act or
Section  20 of the  Exchange  Act)  and  the  officers,  directors,  agents  and
employees of each such  controlling  Person,  to the fullest extent permitted by
applicable  law,  from  and  against  any  and  all  losses,  claims,   damages,
liabilities,   costs  (including,   without  limitation,   reasonable  costs  of
preparation  and  reasonable   attorneys'  fees)  and  expenses   (collectively,
"LOSSES"),  as  incurred,  arising  out of or  relating to any untrue or alleged
untrue statement of a material fact contained in any Registration Statement, any
Prospectus or any form of  prospectus or in any amendment or supplement  thereto
or in any preliminary prospectus,  or arising out of or relating to any omission
or  alleged  omission  of a  material  fact  required  to be stated  therein  or
necessary to make the statements  therein (in the case of any Prospectus or form
of prospectus or supplement  thereto,  in light of the circumstances under which
they were made) not  misleading,  except to the extent,  but only to the extent,
that (1) such untrue  statements or omissions are based solely upon  information
regarding  such  Holder  furnished  in  writing to the  Company  by such  Holder
expressly  for use therein,  or to the extent that such  information  relates to
such Holder or such Holder's  proposed  method of  distribution  of  Registrable
Securities  and was  reviewed and  expressly  approved in writing by such Holder
expressly for use in the Registration Statement, such Prospectus or such form of
Prospectus or in any amendment or supplement  thereto (it being  understood that
the Holder has approved  Annex A hereto for this  purpose) or (2) in the case of
an occurrence of an event of the type specified in Section 3(c)(ii)-(v), the use
by such  Holder of an  outdated or  defective  Prospectus  after the Company has
notified such Holder in writing that the Prospectus is outdated or defective and
prior to the receipt by such  Holder of an Advice or an amended or  supplemented
Prospectus,  but only if and to the extent  that  following  the  receipt of the
Advice or the amended or  supplemented  Prospectus the  misstatement or omission
giving rise to such Loss would have been corrected. The Company shall notify the
Holders  promptly of the  institution,  threat or assertion of any Proceeding of
which the Company is aware in connection with the  transactions  contemplated by
this Agreement.

            (b) Indemnification by Holders. Each Holder shall, severally and not
jointly,  indemnify  and hold  harmless the Company,  its  directors,  officers,
agents and employees,  each Person who controls the Company  (within the meaning
of Section 15 of the Securities Act and Section 20 of the Exchange Act), and the
directors,  officers,  agents or employees of such controlling  Persons,  to the
fullest  extent  permitted by applicable  law,  from and against all Losses,  as
incurred,  arising solely out of or based solely upon: (x) such Holder's failure
to comply with the prospectus delivery requirements of the Securities Act or (y)
any untrue statement of a material fact contained in any Registration Statement,
any  Prospectus,  or any form of  prospectus,  or in any amendment or supplement
thereto,  or  arising  solely  out of or based  solely  upon any  omission  of a
material fact required to be stated  therein or necessary to make the statements
therein not  misleading  to the extent,  but only to the extent  that,  (1) such
untrue statements or omissions are based solely upon information  regarding such
Holder  furnished  in writing to the  Company by such Holder  expressly  for use
therein,  or to the extent that such information  relates to such Holder or such


                                       9
<PAGE>

Holder's  proposed  method of  distribution  of  Registrable  Securities and was
reviewed and expressly  approved in writing by such Holder  expressly for use in
the  Registration  Statement (it being  understood  that the Holder has approved
Annex A hereto for this purpose),  such Prospectus or such form of Prospectus or
in any amendment or supplement thereto or (2) in the case of an occurrence of an
event of the type specified in Section  3(c)(ii)-(v),  the use by such Holder of
an outdated or defective  Prospectus  after the Company has notified such Holder
in writing that the Prospectus is outdated or defective and prior to the receipt
by such Holder of an Advice or an amended or supplemented  Prospectus,  but only
if and to the extent that  following the receipt of the Advice or the amended or
supplemented  Prospectus the  misstatement  or omission giving rise to such Loss
would have been corrected. In no event shall the liability of any selling Holder
hereunder  be  greater  in amount  than the  dollar  amount of the net  proceeds
received by such Holder upon the sale of the Registrable  Securities giving rise
to such indemnification obligation.

            (c) Conduct of Indemnification  Proceedings. If any Proceeding shall
be brought or asserted  against any Person  entitled to indemnity  hereunder (an
"INDEMNIFIED  PARTY"),  such Indemnified  Party shall promptly notify the Person
from whom  indemnity is sought (the  "INDEMNIFYING  PARTY") in writing,  and the
Indemnifying Party shall assume the defense thereof, including the employment of
counsel reasonably  satisfactory to the Indemnified Party and the payment of all
fees and expenses  incurred in connection with defense thereof;  provided,  that
the failure of any  Indemnified  Party to give such notice shall not relieve the
Indemnifying Party of its obligations or liabilities pursuant to this Agreement,
except (and only) to the extent that it shall be finally  determined  by a court
of  competent  jurisdiction  (which  determination  is not  subject to appeal or
further  review)  that  such  failure  shall  have  proximately  and  materially
adversely prejudiced the Indemnifying Party.

            An Indemnified Party shall have the right to employ separate counsel
in any such Proceeding and to participate in the defense  thereof,  but the fees
and expenses of such counsel shall be at the expense of such  Indemnified  Party
or Parties unless:  (1) the Indemnifying Party has agreed in writing to pay such
fees and  expenses;  (2) the  Indemnifying  Party shall have failed  promptly to
assume  the  defense  of  such  Proceeding  and  to  employ  counsel  reasonably
satisfactory to such Indemnified Party in any such Proceeding;  or (3) the named
parties to any such Proceeding  (including any impleaded  parties)  include both
such Indemnified  Party and the Indemnifying  Party, and such Indemnified  Party
shall have been  advised by counsel  that a conflict  of  interest  is likely to
exist if the same  counsel  were to  represent  such  Indemnified  Party and the
Indemnifying  Party (in which  case,  if such  Indemnified  Party  notifies  the
Indemnifying  Party in writing that it elects to employ separate  counsel at the
expense of the Indemnifying  Party,  the  Indemnifying  Party shall not have the
right to assume the defense  thereof and such counsel shall be at the expense of
the  Indemnifying  Party).  The  Indemnifying  Party shall not be liable for any
settlement of any such Proceeding  effected without its written  consent,  which
consent shall not be unreasonably withheld. No Indemnifying Party shall, without
the prior written consent of the Indemnified Party, effect any settlement of any
pending Proceeding in respect of which any Indemnified Party is a party,  unless
such settlement includes an unconditional release of such Indemnified Party from
all liability on claims that are the subject matter of such Proceeding.

                                       10
<PAGE>

            All reasonable fees and expenses of the Indemnified Party (including
reasonable  fees  and  expenses  to  the  extent  incurred  in  connection  with
investigating   or  preparing  to  defend  such   Proceeding  in  a  manner  not
inconsistent  with this  Section)  shall be paid to the  Indemnified  Party,  as
incurred,  within ten Trading Days of written notice thereof to the Indemnifying
Party  (regardless  of whether it is ultimately  determined  that an Indemnified
Party  is  not  entitled  to  indemnification  hereunder;   provided,  that  the
Indemnifying  Party may require such Indemnified Party to undertake to reimburse
all such fees and  expenses  to the extent it is finally  judicially  determined
that such Indemnified Party is not entitled to indemnification hereunder).

            (d) Contribution.  If a claim for indemnification under Section 5(a)
or 5(b) is unavailable  to an  Indemnified  Party (by reason of public policy or
otherwise),   then  each  Indemnifying  Party,  in  lieu  of  indemnifying  such
Indemnified  Party,  shall  contribute  to the  amount  paid or  payable by such
Indemnified  Party  as a  result  of  such  Losses,  in  such  proportion  as is
appropriate  to  reflect  the  relative  fault  of the  Indemnifying  Party  and
Indemnified  Party in connection with the actions,  statements or omissions that
resulted in such Losses as well as any other relevant equitable  considerations.
The relative fault of such  Indemnifying  Party and  Indemnified  Party shall be
determined by reference to, among other things,  whether any action in question,
including any untrue or alleged untrue  statement of a material fact or omission
or alleged omission of a material fact, has been taken or made by, or relates to
information  supplied by, such Indemnifying  Party or Indemnified Party, and the
parties'  relative intent,  knowledge,  access to information and opportunity to
correct or prevent  such  action,  statement  or  omission.  The amount  paid or
payable by a party as a result of any Losses shall be deemed to include, subject
to the limitations set forth in Section 5(c), any reasonable attorneys' or other
reasonable  fees or  expenses  incurred  by such  party in  connection  with any
Proceeding to the extent such party would have been indemnified for such fees or
expenses if the  indemnification  provided for in this Section was  available to
such party in accordance with its terms.

            The parties  hereto agree that it would not be just and equitable if
contribution  pursuant  to  this  Section  5(d)  were  determined  by  pro  rata
allocation or by any other method of allocation  that does not take into account
the equitable considerations referred to in the immediately preceding paragraph.
Notwithstanding the provisions of this Section 5(d), no Holder shall be required
to contribute, in the aggregate, any amount in excess of the amount by which the
proceeds  actually  received  by such  Holder  from the sale of the  Registrable
Securities subject to the Proceeding exceeds the amount of any damages that such
Holder has  otherwise  been  required to pay by reason of such untrue or alleged
untrue statement or omission or alleged omission.

            The indemnity and contribution  agreements contained in this Section
are in addition to any liability that the  Indemnifying  Parties may have to the
Indemnified Parties.

                                       11
<PAGE>

      6. Miscellaneous.

            (a)  Remedies.  In the  event of a  breach  by the  Company  or by a
Holder,  of any of their  obligations  under this Agreement,  each Holder or the
Company,  as the case may be, in  addition to being  entitled  to  exercise  all
rights granted by law and under this Agreement,  including  recovery of damages,
will be entitled to specific performance of its rights under this Agreement. The
Company and each Holder agree that monetary  damages would not provide  adequate
compensation  for any losses  incurred by reason of a breach by it of any of the
provisions of this Agreement and hereby further agrees that, in the event of any
action for specific  performance  in respect of such breach,  it shall waive the
defense that a remedy at law would be adequate.

            (b) No Piggyback on  Registrations.  Except as set forth in Schedule
6(b),  neither  the  Company  nor any of its  security  holders  (other than the
Holders in such capacity pursuant hereto) may include  securities of the Company
in a  Registration  Statement  other than the  Registrable  Securities,  and the
Company  shall not  during the  Registration  Period  enter  into any  agreement
providing any such right to any of its security holders.

            (c) Compliance. Each Holder covenants and agrees that it will comply
with the prospectus delivery requirements of the Securities Act as applicable to
it  in  connection  with  sales  of  Registrable   Securities  pursuant  to  the
Registration Statement.

            (d) Discontinued Disposition.  Each Holder agrees by its acquisition
of such  Registrable  Securities that, upon receipt of a notice from the Company
of the  occurrence  of any event of the kind  described  in Section  3(c),  such
Holder will forthwith  discontinue  disposition of such  Registrable  Securities
under the  Registration  Statement until such Holder's  receipt of the copies of
the supplemented Prospectus and/or amended Registration Statement or until it is
advised in writing (the  "ADVICE") by the Company that the use of the applicable
Prospectus  may be resumed,  and, in either  case,  has  received  copies of any
additional  or  supplemental  filings  that are  incorporated  or  deemed  to be
incorporated  by reference in such  Prospectus or  Registration  Statement.  The
Company may provide  appropriate  stop orders to enforce the  provisions of this
paragraph.  The Company  will use its best efforts to ensure that the use of the
Prospectus may be resumed as promptly as is practicable.  The Company agrees and
acknowledges that any periods during which the Holder is required to discontinue
the disposition of the Registrable  Securities hereunder shall be subject to the
provisions of Section 2(c).

            (e)   Piggy-Back   Registrations.   If  at  any  time   during   the
Effectiveness Period there is not an effective  Registration  Statement covering
all of the Registrable Securities and the Company shall determine to prepare and
file with the  Commission a registration  statement  relating to an offering for
its own account or the account of others under the  Securities Act of any of its
equity securities, other than on Form S-4 or Form S-8 (each as promulgated under
the Securities Act) or their then equivalents  relating to equity  securities to
be issued solely in connection with any acquisition of any entity or business or
equity  securities  issuable in connection  with stock option or other  employee
benefit plans, then the Company shall send to each Holder written notice of such
determination and, if within fifteen days after receipt of such notice, any such
Holder  shall  so  request  in  writing,  the  Company  shall  include  in  such
registration  statement  all or any  part of such  Registrable  Securities  such
holder  requests to be  registered,  subject to customary  underwriter  cutbacks
applicable to all holders of registration rights.

                                       12
<PAGE>

            (f)  Amendments  and  Waivers.  The  provisions  of this  Agreement,
including  the  provisions  of this  sentence,  may not be amended,  modified or
supplemented,  and waivers or consents to departures from the provisions  hereof
may not be given,  unless the same shall be in writing and signed by the Company
and the  Holders  representing  at least a majority of all of the then issued or
issuable Notes and Warrants.  Notwithstanding the foregoing, a waiver or consent
to depart  from the  provisions  hereof with  respect to a matter  that  relates
exclusively  to the  rights of certain  Holders  and that does not  directly  or
indirectly  affect  the  rights of other  Holders  may be given by Holders of at
least a majority of the  Registrable  Securities to which such waiver or consent
relates,  provided,  that the  provisions  of this  sentence may not be amended,
modified,  or  supplemented  except in  accordance  with the  provisions  of the
immediately preceding sentence.

            (g)  Notices.  Any  and  all  notices  or  other  communications  or
deliveries  required or permitted to be provided  hereunder  shall be in writing
and  shall be deemed  given and  effective  on the  earliest  of (i) the date of
transmission,  if such notice or communication is delivered via facsimile at the
facsimile  telephone  number  specified in this Section  prior to 6:30 p.m. (New
York  City  time) on a  Trading  Day,  (ii) the  Trading  Day  after the date of
transmission,  if such notice or communication is delivered via facsimile at the
facsimile telephone number specified in this Agreement later than 6:30 p.m. (New
York City time) on any date and earlier than 11:59 p.m.  (New York City time) on
such date,  (iii) the Trading  Day  following  the date of  mailing,  if sent by
nationally  recognized overnight courier service, or (iv) upon actual receipt by
the party to whom such  notice is  required  to be given.  The  address for such
notices and communications shall be as follows:

         If to the Company:         Calypte Biomedical Corporation
                                    5000 Hopyard Road, Suite 480
                                    Pleasanton, CA 94588
                                    Facsimile No.:  (925) 730-0146
                                    Attn: Chief Financial Officer

         With a copy to:            Coudert Brothers LLP
                                    333 S. Hope St., Ste. 2300
                                    Los Angeles, CA 90071
                                    Facsimile:  (213) 229-2999
                                    Attention:  John A. St.Clair, Esq.


         If to a Investor:          To the address set forth under such
                                    Investor's name on the signature pages
                                    hereto.

         If to any other Person who is then the registered Holder:

                                    To the  address of such Holder as it appears
                                    in the stock transfer books of the Company

                                       13
<PAGE>

or such other  address as may be designated  in writing  hereafter,  in the same
manner, by such Person.

            (h)  Successors  and  Assigns.  This  Agreement  shall  inure to the
benefit of and be binding upon the successors  and permitted  assigns of each of
the parties and shall inure to the benefit of each  Holder.  The Company may not
assign its rights or obligations  hereunder without the prior written consent of
each  Holder.  Each Holder may assign its  respective  rights  hereunder  in the
manner and to the Persons as permitted  under the Purchase  Agreement so long as
such assignment complies with the Purchaser Agreement.

            (i) Execution and  Counterparts.  This  Agreement may be executed in
any number of counterparts, each of which when so executed shall be deemed to be
an original and, all of which taken together  shall  constitute one and the same
Agreement.   In  the  event  that  any   signature  is  delivered  by  facsimile
transmission,  such  signature  shall create a valid  binding  obligation of the
party  executing  (or on whose behalf such  signature is executed) the same with
the same  force and  effect as if such  facsimile  signature  were the  original
thereof.

            (j)  Governing  Law.  All  questions  concerning  the  construction,
validity,  enforcement and interpretation of this Agreement shall be governed by
and construed and enforced in accordance  with the internal laws of the State of
New York,  without  regard to the  principles of conflicts of law thereof.  Each
party agrees that all Proceedings  concerning the  interpretations,  enforcement
and defense of the transactions  contemplated by this Agreement (whether brought
against a party hereto or its respective Affiliates,  employees or agents) shall
be commenced  exclusively in the state and federal courts sitting in the City of
New York, Borough of Manhattan (the "NEW YORK COURTS"). Each party hereto hereby
irrevocably submits to the exclusive jurisdiction of the New York Courts for the
adjudication  of any dispute  hereunder  or in  connection  herewith or with any
transaction  contemplated  hereby or discussed  herein,  and hereby  irrevocably
waives,  and  agrees not to assert in any  Proceeding,  any claim that it is not
personally  subject  to the  jurisdiction  of any New York  Court,  or that such
Proceeding has been commenced in an improper or inconvenient  forum.  Each party
hereto hereby  irrevocably  waives  personal  service of process and consents to
process  being  served in any such  Proceeding  by  mailing a copy  thereof  via
registered or certified  mail or overnight  delivery (with evidence of delivery)
to such party at the  address in effect for  notices to it under this  Agreement
and agrees that such service shall  constitute  good and  sufficient  service of
process and notice thereof. Nothing contained herein shall be deemed to limit in
any way any right to serve  process in any manner  permitted by law.  Each party
hereto hereby irrevocably  waives, to the fullest extent permitted by applicable
law,  any and all  right to trial by jury in any  Proceeding  arising  out of or
relating to this Agreement or the transactions  contemplated  hereby.  If either
party shall commence a Proceeding to enforce any  provisions of this  Agreement,
then the prevailing  party in such  Proceeding  shall be reimbursed by the other
party for its  attorney's  fees and other costs and expenses  incurred  with the
investigation, preparation and prosecution of such Proceeding.

                                       14
<PAGE>

            (k) Cumulative Remedies. The remedies provided herein are cumulative
and not exclusive of any remedies provided by law.

            (l) Severability. If any term, provision, covenant or restriction of
this  Agreement  is held by a court of  competent  jurisdiction  to be  invalid,
illegal,  void  or  unenforceable,  the  remainder  of  the  terms,  provisions,
covenants  and  restrictions  set forth  herein  shall  remain in full force and
effect and shall in no way be affected, impaired or invalidated, and the parties
hereto  shall use their  reasonable  efforts to find and  employ an  alternative
means to achieve the same or substantially  the same result as that contemplated
by such term,  provision,  covenant or restriction.  It is hereby stipulated and
declared to be the  intention of the parties  that they would have  executed the
remaining terms, provisions, covenants and restrictions without including any of
such that may be hereafter declared invalid, illegal, void or unenforceable.

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

            (n) Independent  Nature of Investors'  Obligations  and Rights.  The
obligations of each Investor under this Agreement are several and not joint with
the obligations of each other Investor,  and no Investor shall be responsible in
any way for the  performance of the obligations of any other Investor under this
Agreement.  Nothing  contained  herein or in any  Transaction  Document,  and no
action taken by any Investor pursuant thereto, shall be deemed to constitute the
Investors as a partnership, an association, a joint venture or any other kind of
entity,  or create a  presumption  that the  Investors  are in any way acting in
concert  or as a group  with  respect to such  obligations  or the  transactions
contemplated by this Agreement or any other Transaction Document.  Each Investor
acknowledges  that no other Investor will be acting as agent of such Investor in
enforcing its rights under this  Agreement.  Each Investor  shall be entitled to
independently  protect and enforce its rights,  including without limitation the
rights  arising out of this  Agreement,  and it shall not be  necessary  for any
other  Investor to be joined as an additional  party in any  Proceeding for such
purpose.  The Company  acknowledges that each of the Investors has been provided
with the same  Registration  Rights  Agreement  for the  purpose  of  closing  a
transaction with multiple Investors and not because it was required or requested
to do so by any Investor.

            (o) Independent  Nature of Investors'  Obligations  and Rights.  The
obligations of each Investor under any Transaction  Document are several and not
joint with the  obligations  of any other  Investor,  and no  Investor  shall be
responsible  in any way for the  performance  of the  obligations  of any  other
Investor  under any  Transaction  Document.  The  decision  of each  Investor to
purchase Securities pursuant to the Transaction  Documents has been made by such
Investor independently of any other Investor. Nothing contained herein or in any
Transaction  Document,  and no action  taken by any Investor  pursuant  thereto,
shall be deemed to constitute the Investors as a partnership,  an association, a

                                       15
<PAGE>

joint  venture  or any other kind of entity,  or create a  presumption  that the
Investors  are in any way acting in  concert or as a group with  respect to such
obligations or the transactions  contemplated by the Transaction Documents. Each
Investor  acknowledges  that no other  Investor  has  acted  as  agent  for such
Investor in connection with making its investment hereunder and that no Investor
will be acting as agent of such  Investor  in  connection  with  monitoring  its
investment  in the  Securities  or enforcing  its rights  under the  Transaction
Documents.  Each Investor shall be entitled to independently protect and enforce
its  rights,  including  without  limitation  the  rights  arising  out of  this
Agreement  or  out of the  other  Transaction  Documents,  and it  shall  not be
necessary  for any other  Investor  to be joined as an  additional  party in any
proceeding for such purpose. The Company acknowledges that each of the Investors
has been provided with the same Transaction Documents for the purpose of closing
a  transaction  with  multiple  Investors  and not  because it was  required  or
requested to do so by any Investor.

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                           SIGNATURE PAGES TO FOLLOW]


                                       16
<PAGE>


      IN WITNESS  WHEREOF,  the parties have executed this  Registration  Rights
Agreement as of the date first written above.

                                            CALYPTE BIOMEDICAL CORPORATION


                                            By:
                                               ---------------------------------
                                               Name:  Richard D. Brounstein
                                               Title: EVP and CFO

                   [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK
                     SIGNATURE PAGES OF INVESTORS TO FOLLOW]















                                       17
<PAGE>

      IN WITNESS  WHEREOF,  the parties have executed this  Registration  Rights
Agreement as of the date first written above.

                                     NAME OF INVESTING ENTITY




                                     AUTHORIZED SIGNATORY

                                     By:
                                              ----------------------------------
                                     Name:
                                     Title:

                                     ADDRESS FOR NOTICE

                                     c/o:
                                          --------------------------------------

                                     Street:
                                             -----------------------------------

                                     City/State/Zip:
                                                     ---------------------------

                                     Attention:
                                                --------------------------------

                                     Tel:
                                              ----------------------------------

                                     Fax:
                                              ----------------------------------

                                     Email:
                                              ----------------------------------


                                     With a copy to:

                                     Bryan Cave LLP
                                     1290 Avenue of the Americas
                                     New York, NY 10104
                                     Facsimile No.: (212) 541-4630
                                     and (212) 541-1432
                                     Attn: Eric L. Cohen, Esq.


                                       18
<PAGE>

                                                                         Annex A

                              Plan of Distribution

      The Selling Stockholders and any of their pledgees,  donees,  transferees,
assignees and successors-in-interest  may, from time to time, sell any or all of
their shares of Common Stock on any stock exchange,  market or trading  facility
on which the shares are traded or in private transactions. These sales may be at
fixed or negotiated prices. The Selling  Stockholders may use any one or more of
the following methods when selling shares:

o     ordinary   brokerage   transactions   and   transactions   in  which   the
      broker-dealer solicits Investors;

o     block trades in which the broker-dealer will attempt to sell the shares as
      agent but may  position  and resell a portion of the block as principal to
      facilitate the transaction;

o     purchases by a broker-dealer as principal and resale by the  broker-dealer
      for its account;

o     an exchange  distribution  in accordance  with the rules of the applicable
      exchange;

o     privately negotiated transactions;

o     to cover short sales made after the date that this Registration  Statement
      is declared effective by the Commission;

o     broker-dealers may agree with the Selling Stockholders to sell a specified
      number of such shares at a stipulated price per share;

o     a combination of any such methods of sale; and

o     any other method permitted pursuant to applicable law.

      The Selling  Stockholders  may also sell  shares  under Rule 144 under the
Securities Act, if available, rather than under this prospectus.

      Broker-dealers  engaged by the Selling  Stockholders may arrange for other
brokers-dealers to participate in sales.  Broker-dealers may receive commissions
or discounts from the Selling  Stockholders  (or, if any  broker-dealer  acts as
agent  for the  purchaser  of  shares,  from the  purchaser)  in  amounts  to be
negotiated.  The  Selling  Stockholders  do not  expect  these  commissions  and
discounts to exceed what is customary in the types of transactions involved.

      The Selling  Stockholders may from time to time pledge or grant a security
interest in some or all of the Shares  owned by them and, if they default in the
performance of their secured  obligations,  the pledgees or secured  parties may
offer and sell shares of Common  Stock from time to time under this  prospectus,
or  under  an  amendment  to this  prospectus  under  Rule  424(b)(3)  or  other
applicable  provision of the Securities Act of 1933 amending the list of selling
stockholders to include the pledgee,  transferee or other successors in interest
as selling stockholders under this prospectus.

                                       19
<PAGE>

      Upon the Company being notified in writing by a Selling  Stockholder  that
any material arrangement has been entered into with a broker-dealer for the sale
of Common Stock through a block trade, special offering,  exchange  distribution
or secondary  distribution or a purchase by a broker or dealer,  a supplement to
this prospectus  will be filed,  if required,  pursuant to Rule 424(b) under the
Securities Act,  disclosing (i) the name of each such Selling Stockholder and of
the participating  broker-dealer(s),  (ii) the number of shares involved,  (iii)
the  price  at which  such  the  shares  of  Common  Stock  were  sold,  (iv)the
commissions paid or discounts or concessions  allowed to such  broker-dealer(s),
where  applicable,   (v)  that  such   broker-dealer(s)   did  not  conduct  any
investigation  to verify the information set out or incorporated by reference in
this prospectus, and (vi) other facts material to the transaction.  In addition,
upon the Company being notified in writing by a Selling Stockholder that a donee
or pledge  intends to sell more than 500 shares of Common Stock, a supplement to
this  prospectus  will be filed if then required in accordance  with  applicable
securities law.

      The Selling  Stockholders  also may transfer the shares of Common Stock in
other circumstances, in which case the transferees, pledgees or other successors
in  interest  will  be the  selling  beneficial  owners  for  purposes  of  this
prospectus.

      The  Selling  Stockholders  and any  broker-dealers  or  agents  that  are
involved  in selling  the shares may be deemed to be  "underwriters"  within the
meaning of the Securities Act in connection with such sales. In such event,  any
commissions  received  by such  broker-dealers  or agents  and any profit on the
resale  of the  shares  purchased  by  them  may be  deemed  to be  underwriting
commissions  or discounts  under the  Securities  Act.  Discounts,  concessions,
commissions and similar selling expenses,  if any, that can be attributed to the
sale  of  Securities  will  be  paid  by  the  Selling  Stockholder  and/or  the
purchasers.  Each  Selling  Stockholder  has  represented  and  warranted to the
Company that it acquired the securities  subject to this registration  statement
in the ordinary course of such Selling  Stockholder's  business and, at the time
of its purchase of such securities such Selling Stockholder had no agreements or
understandings,  directly or indirectly,  with any person to distribute any such
securities.

      Each Selling  Stockholder has acknowledged  that Shares registered on this
Registration Statement may not be used to cover short sales of Common Stock made
prior to the date on which this Registration  Statement shall have been declared
effective by the Commission.  If a Selling  Stockholder uses this prospectus for
any sale of the Common  Stock,  it will be subject  to the  prospectus  delivery
requirements of the Securities Act. The Selling Stockholders will be responsible
to comply with the applicable provisions of the Securities Act and Exchange Act,
and  the  rules  and  regulations  thereunder  promulgated,  including,  without
limitation,  Regulation  M,  as  applicable  to  such  Selling  Stockholders  in
connection  with  resales of their  respective  shares  under this  Registration
Statement.

                                       20
<PAGE>

         The Company is required  to pay all fees and  expenses  incident to the
registration  of the shares,  but the Company will not receive any proceeds from
the sale of the Common  Stock.  The Company has agreed to indemnify  the Selling
Stockholders against certain losses, claims, damages and liabilities,  including
liabilities under the Securities Act.






                                       21
<PAGE>

                                                                         Annex B

                         CALYPTE BIOMEDICAL CORPORATION

                 SELLING SECURITYHOLDER NOTICE AND QUESTIONNAIRE

The  undersigned  beneficial  owner of common  stock (the  "COMMON  STOCK"),  of
CALYPTE BIOMEDICAL  CORPORATION (the "COMPANY") understands that the Company has
filed or  intends  to file with the  Securities  and  Exchange  Commission  (the
"COMMISSION") a Registration  Statement for the  registration  and resale of the
Registrable Securities,  in accordance with the terms of the Registration Rights
Agreement,  dated as of April 4, 2005  (the  "REGISTRATION  RIGHTS  AGREEMENT"),
among the Company and the Investors  named therein.  A copy of the  Registration
Rights  Agreement is available  from the Company upon request at the address set
forth below. All capitalized  terms used and not otherwise  defined herein shall
have the meanings ascribed thereto in the Registration Rights Agreement.

The  undersigned  hereby  provides the following  information to the Company and
represents and warrants that such information is accurate:

                                  QUESTIONNAIRE

1.       NAME.

         (a)      Full Legal Name of Selling Securityholder


                  --------------------------------------------------------------


         (b)      Full Legal Name of  Registered  Holder (if not the same as (a)
                  above) through which  Registrable  Securities Listed in Item 3
                  below are held:


                  --------------------------------------------------------------


         (c)      Full Legal  Name of  Natural  Control  Person  (which  means a
                  natural person who directly or indirectly alone or with others
                  has power to vote or dispose of the securities  covered by the
                  questionnaire):


                  --------------------------------------------------------------



2. ADDRESS FOR NOTICES TO SELLING SECURITYHOLDER:

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------


                                       22
<PAGE>

--------------------------------------------------------------------------------
Telephone:
          ----------------------------------------------------------------------
Fax:
    ----------------------------------------------------------------------------
Contact Person:
               -----------------------------------------------------------------

3. BENEFICIAL OWNERSHIP OF REGISTRABLE SECURITIES:

                  Type  and   Principal   Amount   of   Registrable   Securities
                  beneficially owned:


                  --------------------------------------------------------------

                  --------------------------------------------------------------

                  --------------------------------------------------------------



4. BROKER-DEALER STATUS:

         (a)     Are you a broker-dealer?

                                            Yes [_]     No [_]

         Note:   If yes, the Commission's staff has indicated that you should be
                 identified as an underwriter in the Registration Statement.

         (b)     Are you an affiliate of a broker-dealer?

                                            Yes [_]     No [_]

         (c)     If you are an  affiliate  of a  broker-dealer,  do you certify
                 that you bought the  Registrable  Securities  in the  ordinary
                 course of  business,  and at the time of the  purchase  of the
                 Registrable  Securities to be resold, you had no agreements or
                 understandings,  directly  or  indirectly,  with any person to
                 distribute the Registrable Securities?

                                            Yes [_]     No [_]

         Note:   If no, the Commission's staff has indicated that you  should be
                 identified as an underwriter in the Registration Statement.

5. BENEFICIAL  OWNERSHIP OF OTHER SECURITIES OF THE COMPANY OWNED BY THE SELLING
SECURITYHOLDER.

         Except as set forth below in  this Item  5, the  undersigned is not the
         beneficial or  registered  owner of any securities of the Company other
         than the Registrable Securities listed above in Item 3.

                                       23
<PAGE>

                  Type and Amount of Other Securities  beneficially owned by the
                  Selling Securityholder:

                  --------------------------------------------------------------

                  --------------------------------------------------------------

6. RELATIONSHIPS WITH THE COMPANY:

         Except as set  forth  below,  neither  the  undersigned  nor any of its
         affiliates,  officers, directors or principal equity holders (owners of
         5% of more of the equity  securities of the  undersigned)  has held any
         position or office or has had any other material  relationship with the
         Company  (or its  predecessors  or  affiliates)  during  the past three
         years.

         State any exceptions here:


                  --------------------------------------------------------------

                  --------------------------------------------------------------



The  undersigned  agrees to promptly  notify the Company of any  inaccuracies or
changes in the information provided herein that may occur subsequent to the date
hereof and prior to the Effective Date for the Registration Statement.

By signing below, the undersigned  consents to the disclosure of the information
contained  herein in its answers to Items 1 through 6 and the  inclusion of such
information  in the  Registration  Statement  and the  related  prospectus.  The
undersigned understands that such information will be relied upon by the Company
in connection  with the preparation or amendment of the  Registration  Statement
and the related prospectus.

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

Dated:                                    Beneficial Owner:
       --------------------                                ---------------------

                                          By:
                                             -----------------------------------
                                             Name:
                                             Title:

PLEASE FAX A COPY OF THE COMPLETED AND EXECUTED  NOTICE AND  QUESTIONNAIRE,  AND
RETURN THE ORIGINAL BY OVERNIGHT MAIL,

TO: CALYPTE BIOMEDICAL CORPORATION
    (925)730-0146

                                       24