The metabolic effects of intravenous hyperalimentation, using an essential amino acid (EAA) and glucose solution, were evaluated in 2 children with acute renal failure. Hyperammonemia and hyperchloremic metabolic acidosis associated with elevated plasma methionine and depressed plasma citrulline, ornithine, arginine, and histidine levels complicated the nutritional therapy. Initial infusion of a complete amino acid (CAA) solution was not associated with these aberrations and reintroduction of a CAA solution after the EAA trial resulted in a progressive amelioration of or complete recovery from these metabolic disturbances. It is likely that the hyperammonemia was due to an arginine deficiency, while excess methionine and presumably sulfate production may have contributed to the hyperchloremic metabolic acidosis in these two children.