The effects of acute and chronic administration of buprenorphine, an opioid mixed agonist-antagonist, on food-maintained responding were compared in Macaque monkeys. Low acute doses of buprenorphine (0.01 and 0.03 mg/kg) did not change the number of food pellets earned or response rates on an FR 4 (VR 16:S) schedule of reinforcement from saline pre-treatment levels. Acute administration of 0.10 and 0.30 mg/kg buprenorphine significantly suppressed food-maintained responding (p less than 0.01). Chronic buprenorphine self-administration (0.01-0.10 mg/kg/injection) did not significantly suppress food intake, even at total daily doses that were 3 to 9 times higher than the highest dose (0.03 mg/kg) studied in the acute pre-treatment paradigm. Decreases in daily buprenorphine intake to 30 to 40 percent of control levels were not associated with increased food self-administration. Similarly, chronic heroin self-administration (0.01, 0.05, and 0.10 mg/kg/injection) was not associated with significant changes in food self-administration. These data suggest that during chronic self-administration of buprenorphine. Macaque monkeys developed tolerance to its acute suppressive effects on food-maintained responding.