In this 7 year review of the operative records of a single city's teaching hospitals, we found 28 patients with aortoenteric fistulas. Among 25 patients with secondary aortoenteric fistulas, 80 percent presented with a herald bleed. Sepsis was rare. Most diagnostic maneuvers, with the possible exception of upper gastrointestinal tract endoscopy, computerized axial tomography, or ultrasonography, were unhelpful. As noted by others, graft excision, aortic ligature, and extraanatomic bypass is the only predictably useful operative therapy. Initial hospital survival was 60 percent, but this decreased to 36 percent because recurrent aortic complications developed in more than half the initial survivors, 75 percent of whom died. Although the pathogenesis of aortoenteric fistulas remains obscure, our study demonstrates that patients who have previously undergone complicated, repeated, or emergency aortic operations, including previous repair of an aortoenteric fistula, are at high risk for the development of another aortoenteric fistula. Serial screening by noninvasive imaging techniques, such as ultrasonography or computerized axial tomography, may be warranted in these patients.