The aim of this study was to investigate the nitrogen-sparing effect of hypocaloric parenteral nutrition (HPN) with a balanced amino acid supply compared with that of a standard Rose's formula. Eighteen well-nourished patients with colorectal cancer were randomly distributed into 3 groups: I control, II Study group, III Rose's formula. The amount of non-protein calories was similar in both groups: 8 kcal/kg administered as glucose, and 1.33 g of amino acid/kg was also infused during 5 days. There were no differences in the plasma protein levels of total proteins, albumin, and transferrin, but retinol-binding protein was higher in group II compared with the control. Nitrogen balance was significantly better in group II than in group III during the 3rd and 4th days. There were differences in the concentration of aspartic acid and glycine in the plasmatic aminograms between groups II and III. It was concluded that the balanced amino acid solution does not significantly improve a patient's nutritional state. Nor have we observed that the balanced amino acid solution causes fewer modifications in the plasma aminograms. However, it does achieve a slight improvement in the nitrogen balances and the synthesis of retinol-binding protein.