Ten sober adult male subjects, with normal sexual development and function, were examined under basal conditions and after a short-term period (7 days) of alcohol ingestion (200 g/daily). Plasma concentrations of testosterone (T), 17 beta estradiol (E2), progesterone (P) and 17-hydroxyprogesterone (17-OH P) were measured on blood samples drawn before and then every 24 h until the 96th h following a single dose of human chorionic gonadotropin (hCG, 2,000 IU im). Basal plasma T was significantly decreased after short-term ethanol ingestion (p less than 0.01) whereas E2, P and 17-OH P were comparable in both conditions. The magnitude of the T response to hCG injection was significantly lower after ethanol ingestion but still significantly higher than the corresponding one obtainable in chronic alcoholics. At the 7th day of ethanol ingestion plasma LH levels were higher than controls (p less than 0.05). These results demonstrate that short-term ingestion of 200 g ethanol daily can lead to altered testicular response to hCG in normal adult males and corroborate the view that ethanol is a gonadal toxin.