This paper reviews and compares patent pools and intellectual property clearinghouses as alternative systems for efficient access to licensable intellectual property in a 'market for technology' (Arora et al 2001). These systems improve aid downstream research and development by economizing on search and transaction costs faced by licensees, as well as potentially mitigating externalities among owners of complementary intellectual property that lead to the 'tragedy of the anti‐commons' (excessively high license fees). We compare the features and economic effects of different systems, review some successful examples, and suggest directions for future economic research.