All heroin addicts who registered for methadone treatment in Albuquerque in 1969-1971, 1019 in all, were the subjects of this follow-up study, conducted in 1991-1993. The cohort was almost entirely of Hispanic (Chicano) ethnicity, 86% male, with median age 27 at entry. We located 776, dead or alive, and we were able to interview 243 concerning many aspects of their lives. At least one-third of the original group had died during the 22-year period, representing standard mortality ratios 4.0 for males and 6.8 for females. Drug overdose, violence, alcohol, or suicide accounted for nearly all deaths of which the causes were known. Despite the availability of treatment, including methadone maintenance, both heroin use and criminality continued at a high rate. Of the 428 known survivors, 48% were currently enrolled in a methadone program after 22 years. They were using significantly less heroin, alcohol, and other drugs (except nicotine) than those not on methadone. Similar beneficial effects of methadone maintenance were reported retrospectively at interview. Our findings offer an insight into heroin addiction as a chronic lifelong relapsing disease with a high fatality rate.