A randomized controlled trial was conducted from May 1995 to April 1999 in a research clinic in an established drug treatment service. Of 858 volunteers screened, 179 adults with diagnosed opioid dependence were randomized into the study; 154 completed 12 weeks of follow-up. Patients were randomized to MMT (n - 91), which required 2 hours of psychosocial therapy per week during the first 6 months; or detoxification (n - 88), which required 3 hours of psychosocial therapy per week, 14 education sessions, and 1 hour of cocaine group therapy, if appropriate, for 6 months, along with 6 months of (non-methadone) aftercare services. Treatment retention, heroin and cocaine abstinence (by self-report and monthly urinalysis), human immunodeficiency virus (HIV) risk behaviors (Risk of AIDS Behavior scale score), and function in five problem areas (employment, family, psychiatric, legal, and alcohol use (Addiction Severity Index) were compared by intervention group. The study found that methadone maintenance therapy resulted in greater treatment retention (median, 438.5 vs 174.0 days) and lower heroin use rates than did detoxification. Cocaine use was more closely related to study dropout in detoxification than in MMT. Methadone maintenance therapy resulted in a lower rate of drug-related (mean [SD] at 12 months, 2.17 [3.88] vs 3.73 [6.86]) but not sex-related HIV risk behaviors and in a lower severity score for legal status (mean [SD] at 12 months, 0.05 [0.13] vs 0.13 [0.19]). There were no differences between groups in employment, family functioning, or alcohol use. In both groups, monthly heroin use rates were 50 percent or greater, but days of use per month dropped markedly from baseline. The study concluded that these results confirm the usefulness of MMT in reducing heroin use and HIV risk behaviors. Illicit opioid use continued in both groups, but frequency was reduced. Results do not provide support for diverting resources from MMT into long-term detoxification. (publisher abstract modified)