Résumé : A cow's milk supplement providing 500 kcal (2093 kJ) and 18 g of protein a day was given during 2 months to 83 lactating Zairian mothers suffering from protein malnutrition. The mothers′ nutritional status improved significantly after 2 months. The initial 24-hour mother′s milk output was on average 607 ml (s.d.: 182) and did not change significantly after 2 months (604 ml; s.d.: 178). Initial milk output and change in milk output did not differ according to mothers' nutritional status at inclusion. Breast-fed infants showed a significant improvement of their mean serum albumin concentration while their growth was similar to the mean growth of children of the same age.