The reinforcing properties and subjective effects of alcohol were assessed in 29 normal volunteers using a seven-session choice procedure. On the first four sessions, subjects sampled an alcohol (0.5 g/kg) and a placebo beverage twice each. On three subsequent choice sessions, subjects chose the drink they preferred. The number of times they chose alcohol was the measure of its reinforcing properties. On all sessions subjects completed mood questionnaires before and several times after consuming the beverage. Other dependent measures during the experiment included a cognitive performance task, drug liking and identification questionnaires, and breathalyzer alcohol determinations. Demographic and personality data also were obtained. Approximately one-third of the subjects chose the alcohol-containing beverage on all three choice sessions, one-third alternated in their choices of alcohol and placebo, and one-third consistently chose the placebo. When the subjective effects of alcohol (determined during sampling sessions) were compared across the three choice groups, qualitative differences in response to alcohol were observed. For example, alcohol increased elation and vigor scores in the consistent choosers of alcohol, whereas it decreased scores on these measures in the consistent placebo choosers. Consistent alcohol choosers did not differ from placebo choosers in gender or age but they reported more marijuana use and slightly more alcohol use outside the laboratory. They also scored higher on certain measures of arousal and depression, on the Sensation Seeking Scale and on the Psychopathic State Inventory. The results are discussed in terms of individual differences in vulnerability to excessive use of alcohol.