A retrospective review of 275 consecutive patients with symptomatic Crohn disease to determine the frequency and type of bladder involvement yielded 14 cases. All 14 patients had a long standing history of Crohn disease with other positive radiologic features at the time of detection of bladder involvement. Patients were categorized into two groups based on the CT findings: Group I (n = 4) had focal bladder wall thickening adjacent to an extravesical soft tissue mass and/or focal bowel wall thickening; Group II (n = 10) had fistula formation with intravesical air with associated focal bowel wall thickening and/or extravesical soft tissue mass. Bladder involvement in Crohn disease is a progressive pathological process that can result in formation of an enterovesical fistula. The patient may come to radiologic attention at any stage in the course of the disease. Computed tomography is a sensitive and noninvasive method of evaluating the bladder and can be used to identify patients in the prodromal stage who are at risk of developing enterovesical fistulae. Timely intervention may prevent frank perforation into the lumen of the bladder by an inflammatory mass.