Fifty one individuals (37 male and 14 female) were asked to report on the social and behavioral circumstances related to their opiate drug use prior to and during a 90-day methadone detoxification treatment. 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. Of perhaps greater significance, large scale changes were also noted in the frequency of use with others. This decline in use with others was most dramatic with respect to strangers and acquaintances. Implications of these observations for HIV transmission are discussed.