FORM 6-K
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                        REPORT OF FOREIGN PRIVATE ISSUER

                     MITSUI & CO. TO BECOME 20% SHAREHOLDER
                      IN QUINTILES TRANSNATIONAL JAPAN K.K.

                        PURSUANT TO RULE 13a-16 OR 15d-16
                     OF THE SECURITIES EXCHANGE ACT OF 1934


For the month of June 23, 2004


Commission File Number 09929

                               MITSUI & CO., LTD.
                 -----------------------------------------------
                 (Translation of registrant's name into English)


             2-1, OHTEMACHI 1-CHOME CHIYODA-KU, TOKYO 100-0004 JAPAN
             -------------------------------------------------------
                    (Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports
under cover of Form 20-F or Form 40-F:


                      Form 20-F [X]   Form 40-F [ ]


Indicate by check mark if the registrant is submitting the Form 6-K in paper as
permitted by Regulation S-T Rule 101(b)(1): ____


Note: Regulation S-T Rule 101(b)(1) only permits the submission in paper of a
Form 6-K if submitted solely to provide an attached annual report to security
holders.


Indicate by check mark if the registrant is submitting the Form 6-K in paper as
permitted by Regulation S-T Rule 101(b)(7): ____


Note: Regulation S-T Rule 101(b)(7) only permits the submission in paper of a
Form 6-K if submitted to furnish a report or other document that the registrant
foreign private issuer must furnish and make public under the laws of the
jurisdiction in which the registrant is incorporated, domiciled or legally
organized (the registrant's "home country"), or under the rules of the home
country exchange on which the registrant's securities are traded, as long as the
report or other document is not a press release, is not required to be and has
not been distributed to the registrant's security holders, and, if discussing a
material event, has already been the subject of a Form 6-K submission or other
Commission filing on EDGAR.


Indicate by check mark whether by furnishing the information contained in this
Form, the registrant is also thereby furnishing the information to the
Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.


                           Yes [ ]  No [X]




If "Yes" is marked, indicate below the file number assigned to the registrant in
connection with Rule 12g3-2(b): 82- _______



                                   SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned, thereunto duly authorized.


Date: June 23, 2004

                                              MITSUI & CO., LTD.


                                              By: /s/ Tasuku Kondo
                                                 -------------------------------
                                                 Name:  Tasuku Kondo
                                                 Title: Executive Director
                                                        Executive Vice President
                                                        Chief Financial Officer



                                                                   June 23, 2004
For immediate release

                                                              Mitsui & Co., Ltd.

                     MITSUI & CO. TO BECOME 20% SHAREHOLDER
                      IN QUINTILES TRANSNATIONAL JAPAN K.K.

Mitsui & Co., Ltd. ("Mitsui") has agreed with Quintiles Transnational Corp.
("Quintiles") and Quintiles Transnational Japan K.K.("Quintiles Japan"), a
wholly-owned subsidiary of Quintiles, that Mitsui will become a 20% shareholder
in Quintiles Japan in a transaction designed to accelerate Quintiles Japan's
growth and expand Quintiles and Mitsui's strategic alliance capabilities in
pharmaceuticals, biotechnology and healthcare.

Mitsui will acquire the 20% interest in Quintiles Japan by purchasing newly
issued common and preferred shares from Quintiles Japan as well as common shares
from Quintiles. Mitsui's payment for the Quintiles Japan shares will be in the
amount of approximately 8.7 billion yen, with Quintiles having the ability to
receive up to an additional 1.9 billion yen based on Quintiles Japan's future
financial performance. The transaction is subject to satisfaction of customary
contractual conditions and closing is anticipated to occur shortly.

Quintiles helps improve healthcare worldwide by providing a broad range of
professional services, information and partnering solutions to the
pharmaceutical, biotechnology and healthcare industries. Headquartered near
Research Triangle Park, North Carolina, Quintiles has offices in 50 countries
and is the world's leading pharmaceutical services organization. Mitsui is also
an equity owner in Pharma Services Holding, Inc., the parent company of
Quintiles Transnational Corp.

Mitsui intends to become an important partner for Quintiles Japan by
contributing both tangible and intangible business resources such as its vast
network of customers and business partners and effective expertise to develop
strategic customer alliances and generate new investment opportunities in Japan.
Mitsui's aim is to benefit through profitable returns on its equity investments
by helping Quintiles Japan to implement its aggressive plans for growth. This
transaction fits well with Mitsui's goal to invest in first-rate international
companies in the healthcare and service sectors and, in particular, to enhance
those companies' Japanese operations.

As part of this transaction, Mitsui is expected to nominate two directors (one
of whom will be unaffiliated with Mitsui) to a seven-member Quintiles Japan
Board and to provide corporate development assistance to Quintiles Japan through
the addition of one of its executives with extensive corporate development
experience to the Quintiles Japan management team.



                                               Inquiries should be addressed to:
                                               Corporate Communications Division
                                                      Telephone: +81-3-3285-7596
                                                                              Or
                                                     Investor Relations Division
                                                              Mitsui & Co., Ltd.
                                                      Telephone: +81-3-3285-7910
                                                      Facsimile: +81-3-3285-9819