The effect of different doses of ethanol (0.5, 1.0, 2.0 and 4.0 g/kg) on LH, FSH and prolactin levels has been studied in female rats. Ethanol was administered in preovulatory periods (18 hr of diestrous or 9 hr of proestrous) and hormonal levels were measured at the 18 hr of proestrous. Ethanol administered at the 18 hr of diestrous produces a biphasic effect on serum LH levels. High doses of alcohol significantly decreased LH levels, whereas low doses (0.5 g/kg) increased the hormonal levels. When ethanol-treatment was at the 9 hr of proestrous, it only decreased LH levels with the dose of 4.0 g/kg. Serum FSH levels were unaffected by the preovulatory administration of ethanol. Serum prolactin concentrations were significantly elevated after i.p. administration of ethanol at the 18 hr of diestrous and the 9 hr of proestrous. The hyperprolactinemia is more pronounced in the rats treated at the 9 hr of proestrous. The results of these studies suggest that the ability of ethanol to modify LH and prolactin levels is due to a central depression caused for alcohol. These effects of ethanol could be mediated by the hypothalamic releasing factors and/or could be due to a direct action on the pituitary function. The sum of these effects produces important failures of the reproductive function in the female rat.