An association between serum carotenoid concentrations and risk for certain cancers has been observed in epidemiological studies. Determinants of serum carotenoid concentrations are known to include dietary intake, plasma lipid concentrations, and body mass. Menstrual cycle phase, which has not been adequately addressed in previous studies, has been suggested to be a possible additional factor to consider in the interpretation of these values in women. We evaluated hormonal status, serum carotenoids, cholesterol, and triglycerides in 48 healthy women at early follicular, mid-luteal, and late luteal phases of one menstrual cycle. Eating patterns were assessed with diet records at two 3-day intervals during the cycle. Analysis was focused on the 30 subjects who were determined to have ovulated during the menstrual cycle under observation. Serum cholesterol was significantly decreased (P < 0.05) in the late luteal phase of an ovulatory cycle. Lutein concentration was increased in the early follicular phase (P < 0.05) and alpha-carotene was increased in the mid-luteal phase (P < 0.05) only if uncorrected for total cholesterol. Other carotenoids did not vary across the menstrual cycle, whether corrected or uncorrected for total cholesterol concentration. In normal healthy ovulating women, serum carotenoids do not appear to vary with menstrual cycle phase when corrected for serum cholesterol concentrations.