This dissertation investigates resource allocation via institutions. A unifying framework for studying various kinds of institutional structures is provided. After the introductory Part 1, Part 2 presents the general model (Chapter 1) and studies existence of equilibria (Chapter 2). Part 3 provides applications to general equilibrium models under complete markets (Chapter 3), public goods and Lindahl prices (Chapter 4), generalized price systems and sales taxes (Chapter 5), lemons type quality problems (Chapter 6). adverse selection and money (Chapter 7), and a model with Markov technologies and freedom effects on utilities (Chapter 8). welfare implications of most applications are investigated. Chapter 9 discusses further applications and possible future research topics.