A nitrogen balance study was performed in 40 patients with various small-bowel resections. Twenty-two patients had part of or the whole colon in function; 18 had an ileostomy. The patients had body weights that were about 95% of their ideal body weight (range, 133% to 71%). Net nitrogen absorption was significantly lower in patients with extensive small-bowel resection (greater than or equal to 150 cm) (median, 8.0 g/day approximately 64% of the dietary nitrogen intake) compared with patients with small-bowel resection less than 150 cm (median, 9.6/day approximately 82% of the dietary nitrogen intake). No difference in nitrogen balance was observed between the two groups. The median nitrogen balance was not significantly different from zero. No difference in nitrogen absorption, nitrogen balance, or body weight could be demonstrated between patients with part of or the whole colon in function and patients with an ileostomy. We conclude that patients with extensive small-bowel resection may have a significant nitrogen absorption, even in the presence of an ileostomy.