Wheat-soy and corn-soy basal diets designed to be complete in all known nutrients failed to support normal growth and feed efficiency of male broiler chicks to two weeks of age. Highly significant growth responses to these diets were obtained from the addition of faba meal (Vicia faba L.) or of 0.2% Na2SO4. Subsequent studies showed these diets to be deficient in sodium even though they contained, by analysis, 0.13 or 0.14% of sodium. A very low sodium content of the drinking water (3 p.p.m.) is believed to be contributory to this deficient state. A significant growth response was obtained from the addition of 0.2% sodium (0.33% total sodium) whether from NaCl or a combination of NaCl and Na2SO4. These data suggest that it may be important to consider the sodium content of the drinking water when determining the sodium requirement of the chick. A further response was obtained from 5.0 p.p.m. procaine penicillin G suggesting the presence of some toxic substance in the feed ingredients or that a subclinical infection may also have contributed to the poor growth supported by the basal diets.