The longitudinal changes in protein secretion from 27 lactating women(primiparae = 10, multiparae=17) and protein intake of infants have been studied from 0.5 to 6 months postpartum in Chungju and Anseong area. The protein contents o breast milk in primiparae appeared significantly higher than in multipaae at 0.5 and 1 month postpartum. The protein secretion of primiparae and multiparae was not significantly different. In breast-feeding period, there was a tendency that protein secretion from 0.5 to 2 months postpartum was higher than thereafter. Average protein intake of boys from milk from 0.5 to 6 months postpartum was significantly higher than that of girls(p<0.05), because volume of milk intake of boys was much more than that of girls. In the amount of protein intake per infant weight, there was no significant difference between boys and girls. Protein intakes per infant weight decreased during lactation. Mean energy consumption of lactating women was 2,327㎉/day, which was 93.1% of recommended energy allowance for Koreans. Mean dietary protein consumption of lactating women was 81g/day, which was 101.3% of recemmended protein allowance for Koreans. Energy ratio of carbohydrate : protein : lipid was appeared to 68.8 : 13.9 : 17.3.