Book excerpt: This book reflects a large number of intellectual debts that I owe to friends and colleagues. The concepts and methods described here were developed and tested in field projects funded by the United States Agency for International Development. Eric Chetwynd, Jr., played a central role in the Urban Functions in Rural Development (UFRD) projects on which the book is based. Without his advocacy, interest and support for nearly a decade, the projects could not have been undertaken.