Abstract Thirty healthy male volunteers drank ethyl alcohol (1.75 g/kg) from 6 p. m. to 9 p. m., which resulted in hangover the next morning, and 10 subjects served as controls. The twenty subjects, who drank alcohol, received glucose or fructose during the same evening (1.0 g/kg) or on the following morning (0.5 g/kg). In the hangover phase psychomotor performance was recorded by a choice reaction test, two coordination tests and an attention test. The intensity of the hangover was graded subjectively and objectively. Blood ethanol, acetaldehyde and glucose concentrations were analysed. The testing procedure was repeated at 8, 10 and 12 a. m. Ethanol, administered alone, increased significantly the number of mistakes on the choice reaction test in hangover phase, but this effect was abolished by the simultaneous administration of sugar. On the other hand, after the combined administration of ethanol and sugars the number of mistakes and mistake percentage on one coordination test were increased. The etiology on the impaired psychomotor skill during the hangover period is probably not directly related to the pathophysiology of the hangover, as there was no correlation between the impairment of the psychomotor performance and the intensity of the hangover of the subjects.