The increased use of computed tomography (CT) in patients with appendicitis may cause a delay in surgery and, therefore, higher perforation rates. We examined the use of CT, delay in time to surgery, and perforation rates in appendicitis patients operated on in two periods: Phase 1, 1996 through 1998 and Phase 2, 2001 through 2002. CT was performed in 18 per cent of the Phase 1 group compared with 62 per cent in the Phase 2 group. In the Phase 1 group, patients undergoing CT had a delay to surgery compared with those without CT (18.6 hours vs 7 hours; P < 0.0001). In the Phase 2 group, time to surgery was reduced (median time = 12 hours with CT vs 6 hours without CT; P < 0.001). CT was more accurate in the later group; there were less false-negative and equivocal studies. There was no difference in perforation rates between the Phase 1 and 2 groups. Over time, the increased use, efficiency, and accuracy of CT in patients with acute appendicitis were associated with reduced delays to surgery. The use of CT did not harm patients, but did not translate to better overall outcomes in this group of patients.