The diagnostic value of angiography was studied in 116 patients with Crohn's disease. Angiograms showed abnormalities in over 90% of the cases. Many angiographic features were nonspecific; only the "zoning sign" and the presence of paraintestinal mesenteric neovasculature were considered diagnostic. Crohn's colitis could be distinguished from ulcerative colitis in only 30% of the cases. Angiography, as a diagnostic adjunct to barium studies, will reveal the presence of lesions and their extent. This is particularly important in suspected postoperative recurrence of Crohn's disease. Angiography is a potential differential diagnostic aid in doubtful cases of inflammatory and malignant bowel disease.