This paper examines the origins and outlook for the features of the U.S. national innovtion system that have historically distinguished this system from those of other industrial economies. Among these features are (1) the prominent role of antitrust policy; (2) the large share of postwar national R&D expenditures accounted for by government and, within the national governmental R&D budget, the large defense share; and (3) during the postwar period, the significant role of relatively small, new firms in the commercialization of new technologies. The new international economic and technological environment has given rise to a domestic debate over U.S. technology policy that in combination with these elements of change may significantly alter these distiguishing features of the U.S. innovation system.