The intakes of milk and specific nutrients during the first 120 hours after birth were measured in 11 full-term, breast-fed infants. Infants were test weighed at all feeds using an electronic balance, and milk samples were obtained from both breasts one to three times daily. Milk was analyzed for levels of fat, protein, lactose, calcium, sodium, and potassium; energy content was calculated using the Atwater factors. The average (+/- SD) intake of milk in the first 24 hours after birth was 13 +/- 16 g/kg (range, 3 to 32 g/kg), increasing to 98 +/- 47 g/kg (50 to 163 g/kg) and 155 +/- 29 g/kg (110 to 196 g/kg) on days 3 and 5, respectively. Mean daily intakes of energy, lactose, calcium, and potassium were less than 12% of the mean day 5 intake on day 1 and less than 25% of the day 5 intake on day 2. In the first few days after birth, the nutrient intake of the solely breast-fed infant is highly variable and is frequently low.