EXHIBIT 5.1

BLAKE DAWSON WALDRON
                                                        Level 32
           LAWYERS                                      Exchange Plaza
                                                        2 The Esplanade
                                                        Perth WA 6000

                                                        www.bdw.com

                                                        Tel + 61 8 9366 8000
                                                        Fax + 61 8 9366 8111

                                                        DX 169 Perth

                                                        PO Box 7438
                                                        Cloisters Square
                                                        Perth WA 6850
                                                        Australia

                                                        PARTNER
                                                        Roger Davies
                                                        Telephone (08) 9366 8022

                                                        CONTACT
                                                        Alan Gibson
pSivida Limited                                         Telephone (08) 9366 8722
Level 12, BGC Centre
28 The Esplanade
PERTH  WA  6000                                         OUR REFERENCE
                                                        DRD:AJG:09 1395 3581

                                                        28 June 2006



Dear Sirs

REGISTRATION STATEMENT OF FORM F-3  (PRIVATE PLACEMENT)

We have acted as Australian legal advisers to pSivida Limited (COMPANY) in
connection with the Company's registration statement on Form F-3 (REGISTRATION
STATEMENT), originally filed on March 28, 2006 with the Securities and Exchange
Commission under the U.S. Securities Act of 1933 as amended (SECURITIES ACT).
The Registration Statement relates to the sale by the selling shareholders
listed in it of up to 7,315,000 ordinary shares of the Company represented by
731,500 American Depositary Shares issued under a private placement of American
Depositary Shares and warrants (ISSUE). We are furnishing this opinion as
exhibit 5.1 to the Registration Statement, subject to the final paragraph of
this opinion.

1.       DEFINITIONS

         In this opinion:


         (a)      ACN means Australian Company Number.

         (b)      ASIC means the Australian Securities and Investments
                  Commission.

         (c)      ASX means Australian Stock Exchange Limited ACN 008 624 691.

         (d)      COMPANY means pSivida Limited, registered in Western
                  Australia, ACN 009 232 026.

         (e)      CORPORATIONS ACT means the Corporations Act 2001 (Cth).

         (f)      RELEVANT JURISDICTION means the State of Western Australia,
                  Australia.
PERTH
SYDNEY

MELBOURNE
BRISBANE
CANBERRA

LONDON

PORT MORESBY

JAKARTA

SHANGHAI

BLAKE DAWSON WALDRON                                                28 June 2006

pSivida Limited                                                           Page 2
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         (g)      RELEVANT LAWS means the laws of the Relevant Jurisdiction and
                  the federal laws of Australia as they apply in the Relevant
                  Jurisdiction.

         (h)      SELLING SHAREHOLDERS has the same meaning as in the
                  Registration Statement.

         (i)      SUB-COMMITTEE means the sub-committee of the Company's board
                  in relation to the merger with CDS, established by the board
                  of directors of the Company at their meeting held on 13 July
                  2005.

         In this opinion, headings are for convenience only and do not affect
         interpretation and references to paragraphs are to paragraphs of this
         opinion.

2.       DOCUMENTS REVIEWED

         For the purposes of giving this opinion, we have examined the
         following documents:

         (a)      a search of the ASIC database in respect of the Company on 28
                  June 2006 which shows that the Company is registered;

         (b)      the current constitution of the Company;

         (c)      minutes of the meetings of the board of directors of the
                  Company held on 13 July 2005;

         (d)      minutes of the meeting of the Sub-Committee held on 19 August
                  2005; and

         (e)      the Registration Statement.

3.       SCOPE

         This opinion relates only to the Relevant Laws in force at 9.00 am
         (Western Australian time) on the date of this opinion.

         This opinion is given on the basis that it will be construed in
         accordance with the Relevant Laws.

4.       OPINION

         Subject to the assumptions and qualifications set out below, we are of
         the following opinion:

         (a)      the Company has been duly incorporated and is registered as a
                  public company limited by shares under the Corporations Act;

         (b)      the ordinary shares underlying the American Depository Shares
                  to be sold by the Selling Shareholders are legally issued and
                  allotted and fully paid.

BLAKE DAWSON WALDRON                                                28 June 2006

pSivida Limited                                                           Page 3
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5.       ASSUMPTIONS

         For the purposes of this opinion, we have assumed that:

         (a)      if we have reviewed a draft of a document rather than a signed
                  or executed copy, the document will be executed in the form of
                  that draft; and

         (b)      the minutes referred to in paragraphs 2(c) and 2(d) accurately
                  reflect the business transacted at those meetings;

         (c)      no party has contravened or will contravene Chapter 2E
                  (Related party transactions) of the Corporations Act or ASX
                  Listing Rule 10 (Transactions with persons in a position of
                  influence) in connection with the Issue;


         (d)      no party has contravened or will contravene section 260A
                  (Financial assistance for acquiring shares) of the
                  Corporations Act in connection with the Issue;

         (e)      the Company was solvent at the time of and immediately after
                  the Issue and is solvent at the date of this opinion;

         (f)      the meetings of the Company's board of directors and the
                  Sub-Committee to approve the issue of the shares and warrants
                  (and in the case of the board, the appointment of the
                  Sub-Committee) were properly convened and:

                  (i)   the resolutions set out in the minutes referred to in
                        paragraphs 2(c) and 2(d) above were properly passed as
                        valid decisions of the board of directors of the Company
                        and the Sub-Committee (as the case may be) and have not
                        been subsequently revoked, cancelled or varied; and


                  (ii)  the directors of the Company have properly performed
                        their duties and all provisions relating to the
                        declaration of interest and voting were duly observed;

         (g)      where any obligation in connection with the Issue is to be
                  performed in any jurisdiction other than the Relevant
                  Jurisdiction, its performance will not be illegal or
                  unenforceable under the laws of that jurisdiction;

         We have not investigated whether the assumptions in this paragraph 5
         are correct.

         None of the assumptions is limited by reference to any other
         assumption.

6.       QUALIFICATIONS

         Our opinion is subject to the following qualifications.

BLAKE DAWSON WALDRON                                                28 June 2006

pSivida Limited                                                           Page 4
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6.1      SEARCHES

         We have not made any independent investigations or searches, other than
         requests to ASIC for the company search referred to in paragraph 2(a)
         (the information disclosed in the search results rely on information
         lodged by the Company, and the search results may not be complete,
         accurate or up to date).

6.2      GENERAL QUALIFICATIONS


         (a)      We have relied, as to certain matters of fact, on information
                  provided by officers of the Company.

         (b)      This opinion only relates to the laws of the Relevant
                  Jurisdiction. We express no opinion on laws other than the
                  Relevant Laws.

         None of the qualifications is limited by reference to any other
         qualification.

7.       CONSENT

         We hereby consent to the use of this opinion in, and the filing hereof,
         as an exhibit to the Registration Statement and to the reference to our
         firm under the heading "Legal Matters" and elsewhere in the prospectus
         included in the Registration Statement. In giving such consent, we do
         not thereby admit that we come within the category of persons whose
         consent is required under Section 7 of the U.S. Securities Act of 1933,
         as amended, or the Rules and Regulations of the Commission thereunder.

Yours faithfully

/s/ Blake Dawson Waldron