The relationships between fat intake and serum estrone, estradiol, and sex hormone-binding globulin were examined cross-sectionally in 60 premenopausal Japanese women. Blood samples were collected on Day 11 of the menstrual cycle. Intake of fats, classified according to fat type, and other macro- and micronutrients was estimated on the basis of daily diet records from Day 2 through Day 10 of the cycle. Total fat intake was significantly correlated with serum estrone concentration (Spearman r = 0.30, p = 0.02) and marginally significantly correlated with serum estradiol concentration (r = 0.26, p = 0.05) after controlling for age, total energy, and number of days before the next menses. Monounsaturated fat intake was significantly correlated with serum estrone (r = 0.32, p = 0.02) and serum estradiol (r = 0.27, p = 0.045). These data suggest an effect of dietary fat on serum estrogen concentrations.