POWER OF ATTORNEY

Know all by these presents, that the undersigned
hereby constitutes and appoints each of
M. Gay Mather and Dwight W. Rettig, signing
singly, the undersigned's true and lawful
attorney-in-fact to:

(1)execute for and on behalf of the
undersigned, in the undersigned's capacity
as an officer and/or director of National Oilwell
Varco, Inc. (the Company), Forms 3, 4, and 5 in
Accordance with Section 16(a) of the Securities
Exchange Act of 1934 and the rules thereunder;

(2) do and perform any and all acts for and
on behalf of the undersigned which may be
necessary or desirable to complete and execute
any such Form 3, 4, or 5, complete and execute
any amendment or amendments thereto, and timely
file such form with the United States Securities
and Exchange Commission and any stock exchange
or similar authority; and

(3) take any other action of any type
whatsoever in connection with the foregoing
which, in the opinion of such attorney-in-fact,
may be of benefit to, in the best interest of,
or legally required by, the undersigned, it
being understood that the documents executed by
such attorney-in-fact on behalf of the undersigned
pursuant to this Power of Attorney shall be in
such form and shall contain such terms and
conditions as such attorney-in-fact may approve
in such attorney-in-fact's discretion.

The undersigned hereby grants to each such
attorney-in-fact full power and authority to
do and perform any and every act and thing
whatsoever requisite, necessary, or proper
to be done in the exercise of any of the rights
and powers herein granted, as fully to all
intents and purposes as the undersigned might
or could do if personally present, with full
power of substitution or revocation, hereby
ratifying and confirming all that such
attorney-in-fact, or such attorney-in-fact's
substitute or substitutes, shall lawfully do
or cause to be done by virtue of this power
of attorney and the rights and powers herein
granted.  The undersigned acknowledges that
the foregoing attorneys-in-fact, in serving
in such capacity at the request of the undersigned,
are not assuming, nor is the Company assuming,
any of the undersigned's responsibilities
to comply with Section 16 of the Securities
Exchange Act of 1934.

This Power of Attorney shall remain in full
force and effect until the undersigned is no
longer required to file Forms 3, 4 and 5
with respect to the undersigned's holdings
of and transactions in securities issued
by the Company, unless earlier revoked by
the undersigned in a signed writing delivered
to the foregoing attorneys-in-fact.

IN WITNESS WHEREOF, the undersigned has
caused this Power of Attorney to be executed
as of this 19th day of May, 2005.

/s/ Greg L. Armstrong
Signature