In order to investigate the longitudinal changes on zinc secretion of lactating women and zinc intake of breast-fed infants, we examined 20 lactating women(10 primipare and 10 multipare) and their infants during the first 90 days postpartum. We measured the consumed volume of human milk by test-weighing method and zinc concentration by atomic absorption spectophotometry after wet digestion. Weight gain of infants was -5.7, 54.1, 46.3, 42.0 and 32.3g/day at 7, 15, 30, 60 and 90 days postpartum, respectively. The secretion volume of human milk was 527, 608, 724, 841 and 798g/day respectively. The consumed volume of human milk of breast-fed infants was 432, 503, 603, 715 and 715g/day. The intake level of breast milk to secretion volume reached 85.0% in average. The zinc concentration of the milk was 4.29, 3.32, 2.52, 1.62 and 1.18mg/l, and the zinc intake of breast-fed infants was 1.80, 1.69, 1.45, 1.15 and 0.70mg/day. Zine intake per body weight of infants averaged 0.32mg/kg/day during the first 90 days postpartum. The average zinc intake of breast-fed infants was 1.36mg/day, which is 27.2% of the recommended daily allowance for 0-4-month-old infants.