Sublingual buprenorphine (8 mg) was administered to heroin-dependent addicts daily for 18 days and continued from day 19-day 36 either daily or on alternate days. Final data are reported on 18 subjects. The number of self-reported symptoms reviewed as potential adverse drug reactions ranged from 1 to 88 per participant. None was considered to be related definitely to the study medication, and there were no reporting differences between the two dosing regimens. Forty-five reactions were considered probably related to buprenorphine: sedation/drowsiness (three reports) and constipation (42 reports). It was concluded that these were anticipated drug effects rather than adverse reactions. Although some participants showed increases in serum aminotransferase levels, those increases could not be directly attributed to buprenorphine. We conclude that buprenorphine was well tolerated, but further study is needed in this population to delineate the possible attributable risk of the drug to hepatic dysfunction in this population.