The purpose of this report is to illustrate the value of the double contrast technic for the detection of early changes of colitis and for the differentiation between ulcerative and granulomatous colitis. Fifty consecutive patients with radiologically-diagnosed nonspecific colitis are included and the radiographs, endoscopic and pathologic reports and photographs were reviewed. On radiological grounds ulcerative colitis were diagnosed in 23 patients and granulomatous colitis in 27 patients. There were no radiologically indeterminate cases. Follow-up information was obtained by colectomy in nine patients, colonoscopy in nine patients and sigmoidoscopy in the remainder. In no case did the endoscopic or pathologic diagnosis conflict with the radiological diagnosis. With the double contrast technic, very fine mucosal detail can be seen including features such as granular mucosa, "aphthoid" ulcers and discontinuous disease which are not demonstrable by the conventional single contrast barium enema. This detailed mapping of the nature and extent of disease facilitates the differential diagnosis between ulcerative and granulomatous colitis.