Although economists and policy makers have devoted considerable attention to the transfer of technology by U. S.-based multinational firms to their overseas subsidiaries, very little is known about the nature of the technology that is being transferred overseas in this way, the extent to which it leaks out to non-U. S. competitors, the size of the benefits it confers on the host (and other non-U. S.) countries, and the sorts of non-U. S. firms that receive the largest benefits of this sort. This paper presents findings that shed new light on each of these topics.