This study evaluated the effects during hemodialysis of intravenous infusion of amino acids and glucose on plasma amino acid and glucose concentrations and amino acid losses. Eight men undergoing maintenance hemodialysis were each studied during two dialyses using glucose-free dialysate. During one hemodialysis, they were infused with 800 ml of normal saline. During the other hemodialysis, they were infused with an equal volume of water which contained 39.5 g of essential and non-essential free L-amino acids and 200 g of d-glucose. The solutions were infused throughout the dialysis procedure into the drip chamber of the venous outflow from the dialyzer. Subjects were fasted from the night before until the end of hemodialysis, and the order of administration of the two solutions was determined randomly. Plasma essential, non-essential, and total amino acids fell significantly during the infusion of normal saline and rose during the administration of amino acids and glucose. Dialysate total-free amino acid losses averaged 8.2 +/- 3.1 SD g during the infusion of normal saline and 12.6 +/- 3.6 g with the administration of amino acids and glucose. These findings indicate that the intravenous infusion of amino acids and glucose during hemodialysis prevents a fall in plasma amino acid and glucose concentrations and leads to only a slight increase in the losses of free amino acids into dialysate. Because most of the infused amino acids are retained, this technique may be used during hemodialysis to avoid a net outflow of amino acids, minimize disruption of amino acid and glucose pools, and provide a nutritional supplement.