Total serum proteins, albumin, albumin/globulin ratio, and plasma-free amino acids have been determined in 12 small-for-date infants and in 14 normal infants at birth, at 1 week and at 1 month after birth. All infants were fed ad libitum with an adapted infant formula providing 1.9 g protein and 74 kcal/100 ml. Total serum proteins and albumin but not transferrin were low at birth in small-for-date infants, reaching normal values after 1 week of feeding. Serum globulins were low from birth to 1 week in small-for-date infants but they were normal after 1 month. Values for classical amino acid malnutrition indices suggest a state of protein-energy malnutrition which disappeared after 1 week of feeding.