Liver biopsy specimens were studied in 26 patients in whom liver function abnormalities developed during intravenous hyperalimentation (IVH). The clinical manifestations and duration of IVH were evaluated in relation to the morphological changes seen in the liver. Early hepatic changes consisted of fatty metamorphosis, and progressive intrahepatic cholestasis developed as IVH was continued. Essential fatty acid deficiency, amino acid imbalance, caloric excess, and toxic manifestations of certain amino acids are postulated as causative factors. The hepatic steatosis secondary to IVH may be treated by lowering the dextrose concentration of the infusion or by administering dextrose-free amino acid solutions. The clinical importance of this common complication of IVH is the difficulty in distinguishing it from other causes of cholestasis in seriously ill patients.