The literature (55 references) on the symptomatology, pathophysiological mechanisms and the possible role of congeners in the etiology of hangover is briefly discussed. In experimental party settings 91 moderate drinkers (in groups of 4 to 10), aged 21 to 35, of both sexes, drank 1 to 1.75 ml of alcohol per kg as bourbon, or vodka diluted with water. The amount of food and drink taken prior to, during and after alcohol ingestion and dilution and amount of beverage consumed were controlled. Behavioral tests (subtraction series, digit span, speech defect and Romberg sign) were completed before and 75 minutes after beginning to drink. Hangover severity was assessed subjectively on a rating scale and a checklist of symptoms. Blood alcohol levels (by Breathalyzer) 75 min after beginning to drink, ranged from 0.06 to 0.08% after 1.0 ml of alcohol per kg; from 0.10 to 0.12% after 1.25 ml per kg; from 0.08 to 0.15% after 1.5 ml per kg; and from 0.10 to 0.18% after 1.75 ml per kg. No significant differences between the groups receiving vodka or bourbon were observed on the behavioral tests. Only 1 of 10 who had drunk 1.0 ml of alcohol per kg and 2 of 10 who had drunk 1.25 ml per kg reported hangover. At these levels no difference between vodka and bourbon could be discerned with regard to capacity for inducing hangover. Hangover was reported by 33 of 60 who had drunk 1.50 ml per kg and 6 of 11 who had drunk 1.75 ml per kg. Of the 30 vodka drinkers and the 30 bourbon drinkers who had drunk 1.5 ml per kg, 13 and 20, respectively, reported definite hangover and 1 and 10 reported severe hangover. Reasons for the differential effects of the 2 beverages are discussed.