Protein hydrolysate-containing parenteral solutions have been reported to be hepatotoxic. Ten infants who were treated with a 20 percent glucose solution containing either 2.5 percent or 3.25 percent protein hydrolysate are reviewed. Their gestational ages were 30 to 40 weeks and births weights 1000 to 35000 g. Serum glutamate-oxaloacetate transaminase (GOT), glutamate-pyruvate transaminase (GPT), leucine amino peptidase (LAP) and bilirubin were measured serially. Serum amino acids were measured and consistently demonstrated decreased levels of isoleucine and increased aspartic acid, glutamic acid, serine, proline, glycine, alanine, threonine and lysine. The amino acid imbalances were associated with transaminase elevations in eight infants. Serum bilirubin levels increased in six patients and LAP in four. Liver biopsies from three patients showed minimal to moderate hepatic parenchymal disease with cholestasis.