This book confronts the widespread impression that policy or program implementation should be easy, arguing instead that implementation, even under the best of circumstances, is exceedingly difficult. Using the Oakland Project as a case study, this book discusses each stage of the process of implementation, demonstrating that completion of what might seem to be a simple sequence of events will in fact depend on a complex chain of reciprocal interactions. Each part of the chain must be built with the others in view, so the separation of policy design from implementation is fatal. The first four chapters illustrate the movement from simplicity to complexity. Chapter 5 discusses the number of decision points throughout the process, giving an indication of the magnitude of the task. Chapter 6 examines why project targets may be set even if they are unlikely to be met, considering both the position of those who set targets -- top federal officials who wish large accomplishments from small resources in a short time -- and those who must implement them -- career bureaucrats and local participants characterized by high needs and low cohesion. The last chapter discusses the relationship between the evaluation of programs and the study of their implementation, arguing that tendencies to assimilate the two should be resisted.