The physiological consequences of drinking ethanol differ among men and women; however, the biological basis of this gender difference is unknown. Our study characterized sex-related blood ethanol concentration (BEC) 60 min postethanol administration and ethanol elimination rates in male and female monkeys and across the phases of the menstrual cycle. Subjects were male (n = 4) and female (n = 4) cynomolgus monkeys (Macaca fascicularis) with a history of ethanol exposure and maintained at a lean body weight by food restriction. On three separate occasions, each monkey was administered 1.0 g/kg ethanol intragastrically and blood samples (20 microl) were collected every 60 min over a 5-hr period. For females, three phases of the menstrual cycle were determined by the presence of menses and plasma progesterone levels. There was no effect of menstrual cycle on mean 60 min BECs or mean rates of elimination. Mean BECs 60 min after 1.0 g/kg ethanol were: males = 86 mg/dl (+/- 2; n = 4) and females = 82 mg/dl (+/- 5; n = 4). There was no effect of sex on the highest BEC measured, which occurred at the 60 min time point in all subjects. Female monkeys did have faster average rates of ethanol elimination [34 +/- 2 (mg/dl)/hr] compared with males [23 +/- 1 (mg/dl)/hr]. The sex differences in metabolism of ethanol found with the macaque monkey model correlates well with human subject studies and suggests this is an appropriate model to further explore gender differences in response to ethanol.