Serum testosterone, FSH, LH and prolactin levels have been determined in a group of 32 non-cirrhotic heavy drinkers at 9 and 21 h of the 1st, 3rd, 6th, 11th and 15th days after the onset of a florid ethanol withdrawal syndrome. In addition, serum steroid hormone binding globulin (SHBG) levels were determined at the 1st and 15th days. Serum levels of all these hormones were also determined in a control group of 15 healthy male volunteers. Serum testosterone levels, significantly lower in alcoholics at the beginning of the study, progressively increased along the observation period, recovering the circadian rhythm at the end of it. A significant increase was also observed in serum prolactin levels, in the low and upper limits of the normal range at the beginning and at the end of the study respectively. Serum FSH and LH levels were significantly higher in the alcoholics at the beginning of the study, with no significant variations during the observation period. There was a strong relationship between FSH and LH levels, but not between these hormones and testosterone. Thus, our data suggest that ethanol-induced hypogonadism is primary in origin, functional in nature and transient in its evolution.