Utilization of computed tomography (CT) scans in patients with presumed appendicitis was evaluated at a single institution to determine the sensitivity of this diagnostic test and its effect on clinical outcome. Adult patients (age∈>∈17 years) with appendicitis were identified from hospital records. Findings at surgery, including the incidence of perforation, were correlated with imaging results. During a 3-year period, 411 patients underwent appendectomy for presumed acute appendicitis at our institution. Of these patients, 256 (62%) underwent preoperative CT, and the remaining 155 (38%) patients did not have imaging before the surgery. The time interval between arrival in the emergency room to time in the operating room was longer for patients who had preoperative imaging (8.2∈±∈0.3 h) compared to those who did not (5.1∈±∈0.2 h, p∈<∈0.001). Moreover, this possible delay in intervention was associated with a higher rate of appendiceal perforation in the CT group (17 versus 8%, p∈=∈0.017). Preoperative CT scanning in patients with presumed appendicitis should be used selectively as widespread utilization may adversely affect outcomes. The potential negative impact of CT imaging includes a delay in operative intervention and a potentially higher perforation rate. © 2007 The Society for Surgery of the Alimentary Tract.