• Ten patients with protracted diarrhea of infancy received either 8% or 16% of 130 calories/kg/day as amino acids. Patients were treated initially with total parenteral nutrition (TPN) and subsequently with an elemental diet. Nitrogen balance was better during TPN in those who received the higher amino acid intake. No differences were noted between groups in weight gain or restoration of muscle mass. Higher levels of serum urea nitrogen and alkaline phosphatase were noted in patients with the higher amino acid intake; cholestatic liver injury developed in two of these patients. The patients receiving the higher amount of amino acid demonstrated enhanced calciuria during TPN. Other than better nitrogen balance, no clinical benefits and more undesirable side effects were observed in patients receiving 16% amino acid calories.