This research addresses itself to two problematic aspects of methadone maintenance: definition and measure of success of methadone rehabilitation programs and the location and prediction of those features which characterize patients successfully rehabilitated by such programs. For the first time, this research used a differentiated criterion to evaluate success, utilizing five different measures for its evaluation: consumption of methadone, consumption of illicit drugs, group therapy attendance, crime rate, and employment patterns. At the same time, we have theoretically and empirically established that two distinct types of patients exist: the future-oriented and the past-oriented. This time orientation remains constant throughout the patient's stay on the program. Future-oriented patients met with a significantly greater degree of success in the program than past-oriented patients.