The influence of practice while under intoxication was tested on the development of acute tolerance to the motor impairment effect of ethanol. In experiment 1, the motor impairment effect induced by an IP injection of 1.8 g/kg ethanol was quantified after various intervals in separate groups of animals. Lower impairment scores were observed in rats tested at 30 and 45 min after ethanol administration than in those tested at 15 min. In group that was tested repeatedly after ethanol administration, intoxication decreased more rapidly and to a greater extent. The same phenomenon was observed in experiment 2 when a higher dose of ethanol (2.2 g/kg) and later testing (60-180 min after ethanol administration) were employed. To maintain constant blood ethanol levels, those tested at later times received a supplementary dose of ethanol. Impairment scores were lower in rats tested at later times than in those tested earlier. Again, the impairment scores for the practice group decreased more rapidly and to a greater extent. Blood ethanol levels among various groups were essentially the same. Acute tolerance to ethanol can develop without opportunity for practice while under intoxication. Intoxicated practice, however, can facilitate acute tolerance development.