Consisting of a set of closely related studies of urban spatial structure, this monograph focuses on the decentralization of metropolitan areas. Foremost is the belief that decentralization, or suburbanization, lies at the root of most of the social problems that plague urban areas. Therefore, an understanding of the process is basic to policies and programs for mitigating such ills. Professor Mills thus presents an empirical study of the patterns and causes of suburbanization of population and employment from the 1880's to the 1960's. He then constructs theoretical models to analyze the relation between the locations of employment and residence in urban areas as well as the reasons for the increasing move to the suburbs. Special attention is paid to congestion as a cause and effect of the trend towards suburbanization. After considering an idealized model with an economically efficient transportation system, he concludes that a policy of efficient investment and pricing in urban transportation might have a significant effect on the pattern of urban residential density. Finally, a discussion is presented of the ways in which the models could be modified and extended for use in public policy analysis. (BL)