Using original survey data on Japanese small businesses, this paper analyses the impact of the organizational and contractual characteristics of cooperative R&D, such as membership structure, partner relationship, external support, and rules of cost and outcome sharing, on the probability of the technological and commercial success of the project. Empirical results suggest that cooperative R&D is more successful, the higher the quality and quantity of external resources available through cooperation, and the lower the transaction and coordination costs required for such arrangements. Moreover, we found that the determinants of technological and commercial success differ considerably.