The question of why policies fail once adopted, in the words of series editor Stuart Nagel, ′goes to the essence of public policy analysis′. The volume editors, in their extensive and valuable introduction, provide a review of previous efforts to answer aspects of this question and discuss the problems of definition and research political scientists encounter in dealing with it. Louise Comfort in her essay discusses how programme goals must sometimes simply be redifined. Edward Jennings explores the thesis that changes in welfare policy came about largely because of urban unrest. David O′Brien writes aboutt the dilemma confronting agencies caught between the conflicting aims of the Privacy Act and the Freedom of Information Act. Theodore Anagnoson explores the problem of judging a policy that fails because Congress preferred to protect contrary political values.