INTRODUCTION: The aim of this study was to quantify the role of time between symptom onset and surgery on the changing risk of perforation, and to evaluate the possible factors leading to delay to the operation.PATIENTS AND METHODS: The files of 169 patients who underwent appendectomy in our clinic over a two-year period (May 2004-June 2006) were reviewed. The relative risk of perforation was calculated according to the "time-table" method. Time was divided into intervals, initially of 12 hours and, later on, of 24 hours.RESULTS: 18 patients were found to have perforated appendicitis. The time from symptom-onset to first examination ("symptom onset to presentation" time, "SOP" time) was longer for patients with perforation than for those without (p = 0.047). On the other hand, the time from initial examination in the emergency department to the operating room ("ER to OR" time) was shorter for patients with perforation than for those without (p = 0.027). Overall time from symptom onset to operating room, showed no statistical difference between patients with rupture and those without. The risk of perforation was negligible within the first twelve hours of untreated symptoms, but then increased to 8% within the first twenty-four hours. It then decreased to approximately 1.3% to 2% during 36 to 48 hours, and subsequently rose again to approximately 6% (7.6% to 5.8%) for each ensuing 24-hour period. In multivariate analysis, neither the "SOP" nor the "ER to OR" time remained significant contributors to the probability of an individual to suffer from appendiceal perforation.CONCLUSION: When time matters and the risk of adverse outcomes can be reduced, we should change our current approach to care. Surgeons should be mindful of delaying surgery beyond 24 hours of symptom onset in patients with assumed appendicitis.