Exhibit 10.4

TERADYNE, INC.

Amendment

To

1996 Non-Employee Director Stock Option Plan

This Amendment to the 1996 Non-Employee Director Stock Option Plan (the “Plan”),
of Teradyne, Inc., a Massachusetts corporation (the “Company”), is adopted by
resolution of the Board of Directors of the Company (the “Board”) pursuant to a
meeting of the Board dated as of January 22-23, 2007 and effective as of
January 23, 2007 (the “Effective Date”). Paragraph 5. Option Price of the Plan
is hereby deleted in its entirety and replaced with the following as of the
Effective Date:

“5. Option Price. The purchase price of the stock covered by an option granted
pursuant to this Plan shall be 100% of the fair market value of such shares on
the day the option is granted. The option price will be subject to adjustment in
accordance with the provisions of paragraph 10 of this Plan. For purposes of
this Plan, if, at the time an option is granted under the Plan, the Company’s
Common Stock is publicly traded, “fair market value” shall be determined as of
the last business day for which the prices or quotes discussed in this sentence
are available prior to the date such option is granted and shall mean (i) the
closing price (on that date) of the Common Stock on the principal national
securities exchange on which the Common Stock is traded, if the Common Stock is
then traded on a national securities exchange; or (ii) the closing bid price (or
average of bid prices) last quoted (on that date) by an established quotation
service for over-the-counter securities, if the Common Stock is not traded on a
national securities exchange.”