EXHIBIT 5.1

May 20, 2005

ILLUMINA, INC.
9885 TOWNE CENTRE DRIVE
SAN DIEGO, CALIFORNIA 92121

RE: REGISTRATION STATEMENT ON FORM S-8

Ladies and Gentlemen:

      We have acted as counsel to Illumina, Inc., a Delaware corporation (the
"Company"), in connection with the registration statement on Form S-8 to be
filed by the Company with the Securities and Exchange Commission on or about May
20, 2005 (as may be further amended or supplemented, the "Registration
Statement") for the purpose of registering under the Securities Act of 1933, as
amended (the "Act"), the proposed sale by the Company of up to 51,800 shares
(the "Shares") of common stock, par value $0.01 (the "Common Stock"), issuable
by the Company under the CyVera Corporation 2003 Employee, Director and
Consultant Stock Plan (the "Plan").

      We have based our opinion upon our review of the following records,
documents, instruments and certificates:

            1. The Amended and Restated Certificate of Incorporation of the
      Company, as amended to date (the "Certificate"), certified by the Delaware
      Secretary of State, and certified to us by an officer of the Company as
      being complete and in full force and effect as of the date of this
      opinion;

            2. The Bylaws of the Company (the "Bylaws") certified to us by an
      officer of the Company as being complete and in full force and effect as
      of the date of this opinion;

            3. Records certified to us by an officer of the Company as
      constituting all records of proceedings and of actions of the Board of
      Directors and stockholders relating to the assumption of the Plan and the
      reservation of the Shares for issuance pursuant to the Plan;

            4. The Plan; and

            5. Information provided by the Company's transfer agent as to the
      number of shares of the Company's Common Stock outstanding as of May 18,
      2005.

      In connection with this opinion, we have, with your consent, assumed the
authenticity of all records, documents and instruments submitted to us as
originals, the genuineness of all signatures, the legal capacity of natural
persons and the authenticity and conformity to the originals of all records,
documents and instruments submitted to us as copies.

      This opinion is limited to the federal laws of the United States of
America and the Delaware General Corporation Law, and we disclaim any opinion as
to the laws of any other jurisdiction. We further disclaim any opinion as to any
statute, rule, regulation, ordinance, order or other promulgation of any
regional or local governmental body or as to any related judicial or
administrative opinion.

      Our opinion is qualified to the extent that in the event of a stock split,
share dividend or other reclassification of the Common Stock effected subsequent
to the date hereof, the number of shares of Common Stock issuable under the Plan
may be adjusted automatically, as set forth in the terms of the Plan, such that
the number of such shares, as so adjusted, may exceed the number of Company's
remaining authorized, but unissued shares of Common Stock following such
adjustment.



      Based upon the foregoing and our examination of such questions of law as
we have deemed necessary or appropriate for the purpose of this opinion, and
subject to the assumptions and qualifications expressed herein, it is our
opinion that upon payment of the purchase price for the Shares and issuance and
delivery of the Shares pursuant to the terms of the Plan and the stock options
issued under the Plan, the Shares will be legally issued, fully paid and
non-assessable.

      We hereby consent to the filing of this opinion as an exhibit to, and to
the use of this opinion in connection with, the Registration Statement. In
giving this consent, we do not thereby admit that we are within the category of
persons whose consent is required under Section 7 of the Act, the rules and
regulations of the Securities and Exchange Commission promulgated thereunder, or
Item 509 of Regulation S-K.

      This opinion letter is rendered to you and is solely for your benefit.
This opinion letter is rendered as of the date first written above and we
disclaim any obligation to advise you of facts, circumstances, events or
developments which hereafter may be brought to our attention and which may
alter, affect or modify the opinion expressed herein. Our opinion is expressly
limited to the matters set forth above and we render no opinion, whether by
implication or otherwise, as to any other matters relating to the Company, the
Plan or the Shares.

                                                        Very truly yours,

                                                        /s/ Heller Ehrman LLP