The effect of sublingual buprenorphine on cigarette smoking was examined in 23 adult men with DSM III-R diagnosis of concurrent opiate and cocaine dependence. After admission to a clinical research ward, subjects were detoxified with methadone (10-50 mg/day), then were drug-free for 6 days before random assignment to either 4 or 8 mg/day of buprenorphine. Gradually increasing daily sublingual doses of buprenorphine were administered for 5 days, then subjects were maintained on 4 or 8 mg/day of buprenorphine for 12 days. Each subject's preferred brand of cigarettes was available ad libitum throughout the study. Five responses (FR 5) on a key were required to earn each cigarette. The time and number of cigarettes were recorded by an automated cigarette dispenser. Subjects acquired significantly more cigarettes during the buprenorphine induction and maintenance phases (25.5+/-2.0) than during the drug-free phase (18.5+/-1.8; p<0.0002). During buprenorphine induction, the number of cigarettes acquired was positively correlated with increasing doses of buprenorphine (p<0.001) and the inter-cigarette interval was significantly shorter during buprenorphine maintenance than during drug-free conditions (p<0.001). These data showed that daily administration of the partial mu opioid agonist buprenorphine was associated with increased smoking in men concurrently dependent on opiates and cocaine. These findings are consistent with previous reports of opioid-cigarette interactions.