d the actions of the Federal Communications Commission, has affected the entire communications sector, including local telephone networks, long-distance telecommunications, broadband networks, and the Internet. The shift has major implications for economic usage of the communications sector, including informa- tion technology generally and electronic commerce. Understanding the continuing evolution of the telecommunications industry and public policy requires an integrated framework that combines economic and legal analysis. Network economics should be studied in the context of regulatory and legal constraints on market transactions. In turn, the legal aspects of networks should be examined in the context of economic incentives for the establishment and Networks in Telecommunications design of networks. Our discussion offers an integrated framework for analyzing networks in communications. But what is access? We define access as market transactions for the services of networks. In this context, we propose a Coasian theory of networks. Network connections take the form of access when the costs of monitoring and overseeing a particular function within the boundaries of a firm exceed the transaction costs of obtaining those same services from an outside party. The boundaries of a firm's network expand to the point where the incremental costs of internal governance surpass the incremental costs of negotiating and enforcing an external market transaction. In a competitive market, networks have the incentive to establish network boundaries and interconnection arrangements in a way that maximizes economic welfare. Because networks are complex systems, network theory sheds light on the effects of access mandates. The interaction between different network elements can yield sharply discontinuous and unexpected changes in network performance. Accordingly, we apply and extend the graph-theoretic analysis of networks to open the black box of network structure that dominates both current policymaking and legal and economic sc