The relationship between oral contaceptives and ethanol metabolism in women was examined in a group of 40 female social drinkers between the ages of 21 and 30. Twenty women taking oral contraceptives and 20 women not taking oral contraceptives were given a moderate dose of ethanol (0.52 g/kg) during the menstrual, intermenstrual and premenstrual phases of the menstrual cycle. The group of women taking oral contraceptives demonstrated a significantly decreased ethanol elimination rate (105 mg/kg/hr) than the women not taking oral contraceptives (121 mg/kg/hr, p<0.005). Ethanol disappearance rate also was significantly decreased for women taking oral contraceptives (0.015%/hr) than women not taking them (0.019%/hr, p<0.001). These results were consistent across the three phases of the menstrual cycle and when body leanness was taken into consideration. The decreased rate of ethanol metabolism in women taking oral contraceptives is consistent with reports of other drugs having decreased metabolic rates in women taking birth control pills. These results suggest that women taking oral contraceptives should be cautioned concerning their possMe interaction with ethanol, as well as other drugs.