The concept of social capital is defined as a third process (along with individual incentives and authority relationships) for assuring transaction cost efficiency. Social capital is especially relevant to international transactions because cultural differences, large distances, and limited international institutional scope lessen the effectiveness of incentives and authority relationships while social capital can be built within the context of specific international transactions. Methods for building social capital in international settings are explored. A research agenda is articulated as well as a list of managerial implications for using social capital in an international context.