The effect of buprenorphine on the threshold for rewarding brain stimulation to the medial forebrain bundle-lateral hypothalamus was determined in rats using a rate-independent psychophysical method. Increased sensitivity to rewarding brain stimulation (i.e., lowering of the reward threshold) was used as the measure of a drug's reinforcing action. Buprenorphine (SC) produced a significant dose-dependent lowering of the reward threshold, with effective doses varying from 0.004-0.06 mg/kg. These results are consistent with buprenorphine's euphoria producing effects in humans and its ability to sustain self-administration in animals and suggest that buprenorphine may have abuse potential.