Starting with a selection of classical articles on international institutions, this book traces the evolution of regime analysis over the last two decades as a new perspective on international governance. In the process it provides a full account of the major schools of thought that have arisen to account for the demand for international governance, the formation of international regimes, and the effectiveness of international governance systems. By drawing a clear distinction between institutions and organizations and then analysing the relationship between the two, the book clarifies the concept of 'governance without government'. A number of essays explore the probable impact of the proliferation of international regimes on the character of international society. The book's concluding section takes stock of the current status of regime and analyses and assesses emerging challenges in this vibrant field of study.