Plasma levels of LH, FSH, prolactin (PRL), and testosterone (T) were assessed in six normal men following administration of a pharmacologic dose of gonadotropin releasing hormone (GnRH) (500 μg iv over a one-min period) with concomitant oral administration of either ethanol (0.695 g/kg of body weight over a 15-min period) or ethanol placebo. p] Acute ethanol administration had no effect on the response of either LH or FSH to GnRH. PRL levels increased following GnRH and administration of both ethanol and ethanol placebo. Ethanol administration enhanced the T response to GnRH (p < 0.001 vs placebo). During the placebo condition, T levels did not rise significantly until 100 min after GnRH administration, at which time the mean increment over baseline was 101 ± 20 ng/dl (±SEM). In contrast, following ethanol intake, T levels were significantly elevated within 30 min after GnRH administration, at which time the mean increment over baseline was 187 ± 42 ng/dl. The mean T increments were 304 ± 62 and 472 ± 77 ng/dl, respectively, 60 and 105 min following GnRH and ethanol administration. p] The increase in T levels following acute ethanol intake and concomitant gonadotropin stimulation is in contrast to the well-documented effect of chronic ethanol intake on suppression of testosterone synthesis by testicular Leydig cells.