Data were collected from 265 heroin-dependent patients in long-term methadone maintenance treatment for methadone dosage, administration method, illicit drug and problematic alcohol use, psychiatric diagnoses, quality of interpersonal relationships, employment, legal problems, health, and cravings. Patients receiving higher methadone doses (more than 80 mg) were more likely to respond to methadone treatment than patients receiving lower doses. Superior outcome was also related to good quality of interpersonal relationships, stable employment, and lower craving scores. Comorbid psychiatric disorders did not appear to influence methadone effectiveness, but psychopharmacological treatment associated with methadone was associated with a lower rate of urine samples positive for drug use. Administration of methadone weekly or twice weekly ("home methadone") was less effective than daily administration. Although our results were obtained through a descriptive study, which does not permit a prospective evaluation, they suggest the need for higher methadone doses. Job and family relationships appear to be associated, together with psychopharmacological treatment, with a more effective outcome.