The plasma or serum concentrations of testosterone, LH, FSH, PRL, cortisol, 17-hydroxyprogesterone, androstenedione, dehydroepiandrosterone, estrone and estradiol were monitored in 8 healthy male volunteers for a period of 48 hr after administration of one large dose of ethanol (1.75 g/kg BW) within the first 3 hr of the experiment. Each subject served as his own control in an identical experiment without ethanol. Blood alcohol concentration reached a maximum of 1.51 +/- 0.08 g/l (mean +/- SEM) 4 hr after the start of drinking. The maximum decrease in serum testosterone was observed at 12 hr when the serum concentrations of gonadotropins were still unchanged. The decrease in serum testosterone persisted at 24 hr despite increases in the serum levels of LH and FSH. The serum or plasma concentrations of PRL, cortisol, 17-hydroxyprogesterone, androstenedione and dehydroepiandrosterone were clearly increased 4 hr after the start of drinking. The increase in serum cortisol lasted as long as the decrease in serum testosterone. No significant changes were found in plasma concentrations of estrone and estradiol. Our results suggest that in addition to direct testicular effects of alcohol, increased adrenal secretion of cortisol may contribute to the decrease in serum testosterone in men acutely intoxicated with ethanol.