Exhibit 5

                   [Simpson Thacher & Bartlett LLP Letterhead]

                                                                  March 23, 2004

Communications & Power Industries, Inc.
811 Hansen Way
P.O. Box 51110
Palo Alto, California 94303-1110

Ladies and Gentlemen:

         We have acted as counsel to Communications & Power Industries, Inc., a
Delaware corporation (the "Company"), and to CPI Holdco, Inc., a Delaware
corporation, CPI Subsidiary Holdings Inc., a Delaware corporation,
Communications & Power Industries International Inc., a Delaware corporation,
and Communications & Power Industries Asia Inc., a Delaware corporation
(collectively, the "Guarantors"), in connection with the Registration Statement
on Form S-4 (the "Registration Statement") filed by the Company and the
Guarantors with the Securities and Exchange Commission (the "Commission") under
the Securities Act of 1933, as amended, relating to the issuance by the Company
of $125,000,000 aggregate principal amount of 8% Senior Subordinated Notes due
2012 (the "Exchange Securities") and the issuance by the Guarantors of
guarantees (the "Guarantees") with respect to the Exchange Securities. The
Exchange Securities and the Guarantees will be issued under an indenture dated
as of January 23, 2004 (the "Indenture") among the Company, the Guarantors and
BNY Western Trust Company, as trustee (the "Trustee"). The Exchange Securities
will be offered by the Company in exchange (the "Exchange") for $125,000,000
aggregate principal amount of its outstanding 8% Senior Subordinated Notes due
2012.

         We have examined the Registration Statement and the Indenture, which
has been filed with the Commission as an exhibit to the Registration Statement.
We also have examined the originals, or duplicates or certified or conformed
copies, of such corporate records, agreements,



COMMUNICATIONS & POWER INDUSTRIES, INC.

                                                                  March 23, 2004

                                       -2-

documents and other instruments and have made such other investigations as we
have deemed relevant and necessary in connection with the opinions hereinafter
set forth. As to questions of fact material to this opinion, we have relied upon
certificates or comparable documents of public officials and of officers and
representatives of the Company and the Guarantors.

         In rendering the opinions set forth below, we have assumed the
genuineness of all signatures, the legal capacity of natural persons, the
authenticity of all documents submitted to us as originals, the conformity to
original documents of all documents submitted to us as duplicates or certified
or conformed copies and the authenticity of the originals of such latter
documents. We also have assumed that the Indenture is the valid and legally
binding obligation of the Trustee.

         Based upon the foregoing, and subject to the qualifications,
assumptions and limitations stated herein, we are of the opinion that:

                  1.       When the Exchange Securities have been duly executed,
         authenticated, issued and delivered in accordance with the provisions
         of the Indenture, the Exchange Securities will constitute valid and
         legally binding obligations of the Company enforceable against the
         Company in accordance with their terms.

                  2.       When the Exchange Securities have been duly executed,
         authenticated, issued and delivered in accordance with the provisions
         of the Indenture upon the exchange and the Guarantees have been duly
         executed and issued, the Guarantees will constitute valid and legally
         binding obligations of the Guarantors enforceable against the
         Guarantors in accordance with their terms.

         Our opinions set forth above are subject to (i) the effects of
bankruptcy, insolvency, fraudulent conveyance, reorganization, moratorium and
other similar laws relating to or affecting creditors' rights generally, (ii)
general equitable principles (whether considered in a proceeding in equity or at
law) and (iii) an implied covenant of good faith and fair dealing. We express no
opinion with respect to any severability provisions contained in the Exchange
Securities or the Guarantees.



COMMUNICATIONS & POWER INDUSTRIES, INC.

                                                                  March 23, 2004

                                       -3-

         We are members of the Bar of the State of New York, and we do not
express any opinion herein concerning any law other than the law of the State of
New York, the federal law of the United States and the Delaware General
Corporation Law (including the statutory provisions, all applicable provisions
of the Delaware Constitution and reported judicial decisions interpreting the
foregoing).

         We hereby consent to the filing of this opinion letter as Exhibit 5 to
the Registration Statement and to the use of our name under the caption "Legal
Matters" in the Prospectus included in the Registration Statement.

                                            Very truly yours,

                                            /s/ Simpson Thacher & Bartlett LLP

                                            SIMPSON THACHER & BARTLETT LLP