This research project focuses on the workings of imperfect competition. More specifically, the project adds to the analysis of the following key issues in modern industrial organization and regulation: (i)The workings of imperfect competition in vertically-related industries, where several firms are involved in manufacturing, distributing, and marketing the final product; (ii)The competitive effects of restructuring network industries, where the final product is distributed over a network infrastructure (e.g., telecommunications, electricity, railways, etc.);(iii)The theoretical and empirical foundations of competition policy. A key motivation for this project is the fact that competition authorities are increasingly faced with complex cases of alleged misconduct, especially in network and vertically-related industries, where the available economic literature offers little guidance. An important problem is the fact that many of the relevant game-theoretic models are not robust to subtle changes in assumptions or have never been subjected to thorough empirical testing. Consequently, this research project incorporates both theoretical and empirical work.