The effects of ethanol administration (0, 0.25, 0.5, 0.75 and 1.0 g/kg intraperitoneal) were examined in a conflict test in 24 alcohol-preferring (P)-rats, 17 alcohol-nonpreferring (NP)-rats, and 24 heterogeneous Wistar rats. The conflict test was a modified Geller-Seifter procedure employing an unpunished random interval 30-sec component and an incremental shock conflict component. Heterogeneous Wistar rats displayed significant increases in punished responding with doses of 0.5, 0.75, and 1.0 g/kg of ethanol. P-rats did not show a significant increase in punished responding until 0.75 g/kg ethanol. NP rats displayed significant increases in punished responding with all doses tested (0.25, 0.5, and 0.75 g/kg). There were no group differences in the effects of ethanol on unpunished responding. Thus NP-rats were more sensitive and P-rats were less sensitive to the anticonflict effects of ethanol than heterogeneous Wistar rats. The results suggest that the P and NP rats may show a profile of sensitivity to the anticonflict effects of ethanol similar to the sensitivity to the intoxicating effects of ethanol observed in family history positive and family history negative human subjects.