Mature human milk composition was determined from monthly samples collected from five, healthy, Caucasian, lactating women. A 72-hour dietary record was kept monthly from the twelfth week of pregnancy to the sixth month postpartum. Nutrient content of milk samples was similar to values reported in the literature. Calcium and zinc concentrations of human milk decreased significantly during the five month study. Moisture, energy, total lipids, protein, and magnesium levels remained fairly constant over the course of lactation. Dietary intake during pregnancy was not significantly correlated with nutrient concentration in human milk. For dietary intake during lactation, a significant correlation was observed between caloric intake and energy content of human milk for the second month of lactation. A significant correlation was observed between protein intake and protein content in the milk for the sixth month of lactation. Zinc concentration was significantly correlated with dietary intake during the fourth month of lactation. No other significant correlation was observed between nutrient content of human milk and dietary intake during the lactation period. / M.S.