Plasma and erythrocyte zinc levels were estimated in children suffering from protein-calorie deficiency. Plasma zinc levels were low on admission and returned to normal levels after nutrition rehabilitation. Values in kwashiorkor were lower than those in marasmus. Erythrocyte zinc concentration was unaltered. Significant amounts of zinc were also found in oedema fluid. It is suggested that the lowered plasma zinc levels in kwashiorkor and marasmus may be due to decreased levels of metal-binding protein and due to poor availability of dietary zinc from the habitual cereal-based diets. The further lowering of plasma zinc in kwashiorkor may be due to the added loss of zinc into the interstitial compartment.