This study was conducted to investigate the relationship between lactational capacity and intakes of energy and energy-yielding nutrients. Food consumption, intakes of carbohydrate, protein, fat and energy and quantity and proximate composition of milk of 11 lactating Korean mothers were determined at 1, 2 and 3 months postpartum longitudinally. Food consumption was estimated using a 24-hour recall method ; intakes of energy and energy-yielding nutrients were calculated according to the Food Composition Table. Daily milk production was estimated using a 72-hour test-weighing method ; protein, fat, lactose and energy concentrations were analyzed. Average intakes of energy and protein were 1974$pm$386㎉/day and 67.0$pm$12.3㎉/day, these were 73% and 74% of the Korean Recommended Allowances, respectively. Average milk yield was 720.1$pm$123.3ml/day containing energy 59.6$pm$9.5㎉/dl, protein 1.1$pm$0.1g/dl, fat 2.7$pm$0.8g/dl, and lactose 6.3$pm$0.3g/dl. No relationship existed between the intakes of carbohydrate, protein, fat and energy and the quantity and proximate composition of the milk. However, the intakes of energy, carbohydrate and vegetable protein were inversely related to the concentrations of energy and lactose in the milk. This result indicates that lactational capacity may be affected by the other factors excluding intakes of energy and energy-yielding nutrients and a high intake of energy may not guarantee optimal lactational capacity.