With the recognition of a functional relationship between anti-social behavior and the environment in which it occurs, and hence of the appropriateness of environmental intervention, there has been an increasing appeal for the use of behavior modification with criminals and delinquents. This has led to the development of many sound programs in the area of prevention and rehabilitation. Two programs of each type are described. At the same time, however, there are several issues which presently plague the effectiveness of behavior modification. In general, these issues relate to the need to establish behavior modification programs on an empirical or analytical basis, the need to focus upon possible side effects which are incompatible with long-range goals, and finally the need to go beyond a demonstration of the power of behavior modification and focus on problems of generalization, bringing the behavior under the control of natural contingencies. (Author/KS)