Background: The aim of this study was to elucidate the natural history of appendicitis. Methods: Data was collected prospectively from consecutive patients admitted to hospital for acute abdominal pain. The degree of appendiceal inflammation in relation to preoperative duration of pain was analysed. Results: The study comprised 253 patients operated on for acute appendicitis that could recall the onset of abdominal pain. There was a longer duration of pre-hospital pain in patients, irrespective of age, with perforated appendicitis compared to patients with phlegmonous or gangrenous appendicitis (p < 0.001). In the multivariate analysis, patient age and preoperative duration of pain were independent risk factors for perforation. Conclusion: Patient delay in presentation is the predominant factor determining the incidence of complicated appendicitis, and this delay is not influenced by age or gender.