EXHIBIT 5.1

                                 BRYAN CAVE LLP
                           1290 AVENUE OF THE AMERICAS
                            NEW YORK, NEW YORK 10104

                                                        November 3, 2005
Activision, Inc.
3100 Ocean Park Boulevard
Santa Monica, California 90405

Re:  Activision, Inc.
Registration Statement on Form S-8

Ladies and Gentlemen:

We are rendering this opinion in connection with the registration by Activision,
Inc., a Delaware corporation (the "Company"), of 1,600,000 shares (the "Shares")
of its Common Stock, par value $.000001 per share, under the Securities Act of
1933, as amended (the "Securities Act"), pursuant to the above-referenced
Registration Statement on Form S-8 filed with the Securities and Exchange
Commission on November 3, 2005 (the "Registration Statement"). The Shares are
reserved for issuance upon the exercise of options or other awards granted under
the Company's 2002 Employee Stock Purchase Plan (the "Plan").

We are familiar with the Amended and Restated Certificate of Incorporation, as
amended, and the Second Amended and Restated By-laws of the Company and have
examined copies of the Registration Statement, the Plan, the resolutions adopted
by the Company's Board of Directors, and originals or copies, certified or
otherwise identified to our satisfaction, of such other documents, evidence of
corporate action, certificates and other instruments, and have made such other
investigations of law and fact, as we have deemed necessary or appropriate for
the purposes of this opinion.

Based on the foregoing, and upon such further investigation as we have deemed
relevant, we are of the opinion that the Shares, when issued in accordance with
the terms of the Plan, including payment of the applicable purchase price, will
be duly authorized, validly issued, fully paid and nonassessable.

We consent to the filing of this opinion as an exhibit to the Registration
Statement relating to the Shares and to the use of our name wherever appearing
in the Registration Statement and any amendment thereto. In giving the foregoing
consent, we do not admit that we are in the category of persons whose consent is
required under Section 7 of the Securities Act or the rules and regulations of
the Securities and Exchange Commission promulgated thereunder.

Very truly yours,

BRYAN CAVE LLP