Since 1967, 170 heroin addicts have used methadone-based maintenance therapy. The experimental programme, confined to the Uppsala Psychiatric Clinic, followed the Dole-Nyswander method. Evaluation of the results shows the therapy to be successful in reducing mortality and permanent disability rates in heroin users. In addition it was found that addicts included in the programme were more likely to achieve complete social rehabilitation. In spite of much criticism, the experiment was sufficiently successful to justify its continuation, though still within the limits and along the lines adopted in the past.