&NA;Samples of maximally diseased and adjacent macroscopically normal intestine from 52 patients undergoing surgery for Crohn's disease were analyzed for ascorbate content; 26 of the patients had intestinal fistulas and 26 did not. Ascorbate analyses were also performed on samples of normal intestine from ten control patients. Diseased intestine from both groups of patients with Crohn;s disease contained significantly more ascorbate than the adjacent macroscopically normal intestine. Their diseased intestine also contained significantly more ascorbate than normal intestine from controls. Whereas diseased intestine from patients without fistulas contained 47 percent more ascorbate than their normal intestine (P<.001*), the diseased intestine from patients with fistulas contained only 23 percent more ascorbate than their normal intestine (P<.02*). Patients with fistulas appear unable to concentrate as much ascorbate in their diseased intestine as patients without fistulas. This difference may be a factor in the pathogenesis of fistula formation in Crohn's disease because of the importance of ascorbate in collagen production.