During the late 1980's, police and health officials led interagency partnerships to develop several large methadone maintenance programs. The programs engaged up to 5,000 people at a given point in time and appeared to stabilize the heroin problem and significantly reduce the amount of drug-related crime. As part of program evaluation, data were obtained from clinic records, self-report questionnaires, and interviews with a treatment sample of 209 clinic patients who participated in methadone maintenance. Data on clinic patients were compared with data on a sample of heroin only and polydrug users in the community who did not receive methadone. Substantial reductions in illicit drug use and acquisitive crime were evident after methadone maintenance. The community sample used far more illicit drugs than the treatment sample, with heroin, cocaine, and crack dominating. A historical overview of recorded crime and illicit drug use in Merseyside is presented. The efficacy of methadone maintenance programs and their implications for law enforcement are discussed. 46 references, 9 tables, and 3 figures