International co-operation in criminal law enforcement has become a centrally important policy issue for Europe in the 1990s. In criminal matters, when a decision is taken to go beyond the discretionary exchange of information towards institutionalized police co-operation, a whole Pandora's box of issues and problems is opened. This book, based on interviews in a wide variety of documentary sources, examines the progress of this co-operation. The authors cover all the major and theoretical issues associated with the emerging pattern of co-operation, including the harmonization of criminal law and criminal procedure, law enforcement strategies, police organization and discipline, and the politics of immigration and civil liberties. In a European Union without internal border controls there is widespread agreement on the objective of closer police co-operation. But prospects in some areas are not good and there are potential pitfalls, even dangers, along the road to more integrated arrangements. The authors conclude by making recommendations that proper accountability arrangements are a prerequisite of a balanced and efficient system of European police co-operation.