Using tests for cognitive performance (the Pauli test) and psychomotor coordination (the Pursuit Rotor test), the interaction between the drinking history of the subjects, the alcohol dose, and acute alcohol tolerance were examined in light and moderate alcohol consumers (N = 10). Both groups of subjects were tested with doses of alcohol corresponding to 0.5 and 1.0 g/kg. Dose order was random and tests were carried out at an interval of 1 week. Reports of the subjects' previous experience with alcohol indicated that the moderate consumers ingested alcohol in higher quantities than the light consumers. The light consumers were rather inexperienced with frequent alcohol consumption at the quantities investigated, as were the moderate consumers for the higher of the alcohol doses used. Acute tolerance was assessed by comparing performance at equal concentrations of alcohol on the ascending and the descending limbs of the alcohol concentration curve. In the test for cognitive performance, both doses of alcohol in light alcohol consumers yielded significant differences between the ascending and descending limbs of the alcohol concentration curve, suggesting the existence of acute tolerance. In the moderate alcohol consumers, only a tendency to acute tolerance was observed for the higher of the doses tested. In the test for the psychomotor performance, both of the measures of frequency (of misses) and duration (of time outside the target area) were used. The results showed that in the light consumers, acute tolerance was seen for both of the doses, and to some extent for both of the dependent measures (frequency and duration) investigated. However, in the moderate alcohol consumers, acute tolerance was only observed for the higher of the doses and only for the duration measure. Given the difference in drinking history between the two groups of subjects, the implication would be that when the dose of alcohol exceeds the subjects' prior experience, acute tolerance seems inevitable. The present results clearly demonstrate the complexity of the acute tolerance phenomenon, and emphasize the fact that the results are dependent on the subjects' prior experience with alcohol as well as the dose of alcohol ingested, and consequently suggest the interaction between acute and chronic alcohol tolerance.