Interlocking Directorate Act of 1989

Amends the Clayton Act to prohibit any person from serving as a director or officer (currently director only) of any two corporations if each (currently any) such corporation has capital, surplus, and undivided profits aggregating more than $10,000,000 (currently $1,000,000) and such corporations are competitors, so that the elimination of competition by agreement between them would constitute a violation of any of the provisions of the antitrust laws. Establishes exceptions to such prohibition when: (1) the aggregate competitive sales of either corporation are less than $1,000,000; (2) the aggregate competitive sales of either corporation are less than one percent of that corporation's total sales; or (3) the aggregate competitive sales of each corporation are less than four percent of that corporation's total sales. Increases or decreases the $10,000,000 and $1,000,000 threshold amounts by the percentage increase or decrease in the gross national product for the preceding fiscal year. Provides that a director or officer shall not be deemed ineligible under the provisions of this Act until the expiration of one year from the date an event causing ineligibility occurred, or, if practical, the next regularly scheduled election of directors, whichever occurs first.