The behavioral circumstances related to opiate drug use were examined during a 90-day out-patient methadone detoxification. Seventy-one subjects (55 male and 16 female) were followed from the day of intake to treatment termination. Data were collected by means of a weekly structured interview. Questions were asked about each occasion of opiate use in the previous week with respect to time, source, cost, social circumstance, etc. Monitored urine samples were tested x 3/week to verify verbal reports. The study demonstrated beneficial effects of the detoxification treatment by showing dramatic decreases in rates and amounts of opiate drug use during treatment. The study also identified race (p less than .0008; t = -3.522; beta = -0.366), gender (p less than .0243; t = 2.305; beta = 0.222), and the number of opiate use episodes/week at baseline (p less than .0013; t = -3.364; beta = -0.338) as significant and independent predictors of treatment outcome. Current duration of regular and continuous opiate use was also found to be marginally significant. The overall regression was highly significant (p less than .0001; F = 9.176; df = 4,66). A second regression analysis with race, age, and gender excluded as independent variables was conducted in order to derive indices which were related to behavioral and environmental characteristics versus global physical/cultural identification. With race and gender removed, the overall regression was still highly significant, although less than a fifth of the variance was accounted for. The number of opiate use episodes/week at baseline and the total number of drug-related stimulus cue exposures at baseline were found to be independently significant variables in the analysis. Knowledge of the impact of such behavioral factors on the treatment process may enable us to better understand the role of environmental contributors to opiate use. Such information may also help us to direct our limited resources and to better focus our treatment interventions.