Acute ethanol toxicity was evaluated in genetically defined mice by employing the conditioned-flavor-aversion paradigm. Mice of the C57BL/6 and BALB/c strains, and the F1 cross between C57BL/6 males and BALB/c females, were accustomed to consume water during daily 4-hour periods of availability. Saccharin solution (0.1% w/v) was then substituted for water and 4 hours later each mouse received ethanol (0, 1.5, 3.0, 4.5, or 6.0 g/kg b. wt) via gastric intubation. Beginning one week later, saccharin intake was measured during 24-hour periods of availability at weekly intervals for 4 weeks. C57BL/6 and F1 mice that had not received ethanol consumed less saccharin than respective control mice that had not received ethanol. The decrease in saccharin intake was generally related to the dose and gradually diminished over subsequent exposures to saccharin without ethanol. Saccharin intake in BALB/c mice that had received ethanol did not differ from the intake of control mice. These data suggest that genetic variables may determine the extent to which toxicant-induced conditioned flavor aversions can be established in mice.