We compared urinary and fecal excretions of fluid, electrolytes, and nutrients in six patients with a high jejunostomy during three randomized consecutive 3-day periods of total enteral nutrition with three diets differing only by the degree of hydrolysis of the protein moiety: whole proteins, their hydrolysate (63% nitrogen as small peptides with < 1000 M), and the two mixed together. Daily nitrogen absorption was significantly enhanced with the small-peptide and mixed diets (14.3 +/- 3.4 and 13.1 +/- 2 g, respectively) compared with the whole protein diet (10.9 +/- 2.4 g, p = 0.012). Concomitantly, blood urea nitrogen and urinary urea excretion increased with the small-peptide diet. Apparent absorption of fat and calories, fecal weight, and urinary and fecal excretions of sodium, potassium, calcium, and magnesium remained unchanged. We conclude that a small-peptide-based diet may be beneficial in patients with short-bowel syndrome.