Four clinical experimental studies will be conducted which may demonstrate improved methods of retaining opioid-dependent persons in treatment on methadone maintenance. The effects of four treatment innovations on retention and rehabilitation will be studied. In addition, because intravenous drug users are at increased risk for HIV infection due to needle sharing and unsafe sexual practices, the effects of treatment on AIDS risk behavior will be assessed. The four treatment innovations to be studied include: elimination of patient fees, extended dispensing hours, patient-regulated methadone dose, and optional counseling. In each study 15 opioid-dependent patients admitted to methadone maintenance will be randoml assigned to experimental and control groups. . Both groups will have the same treatment, except that the experimental group will have the treatment innovation. The groups will be compared on several outcome variables, including months retained in treatment, intravenous use of illicit drugs, employment, criminality, needle sharing, and sexual practices. Multivariate analyses will be conducted in an attempt to estimate to what extent the background variables predict outcomes.