This paper seeks to examine the evidence of causal links between drug -misuse, particularly heroin, and criminal behaviour. While it is generally accepted that such a link*exists, the question is asked whether the treatment of drug misuse has an effect on levels of drug misuse and on criminal activity. The value of methadone treatment as one of several treatment modalities, is examined in this context. The author does not wish to advocate one form of treatment over another but merely to investigate what can be gained from a study of the literature.