A prospective study with long-term follow-up was undertaken of 248 patients (137 males, median age 18 years (range 6-81 years), undergoing emergency appendicectomy during a 12-month period. Acute inflammation was present in 182 patients (73.4%) (males 86.1%, females 57.8%; P < 0.001). Before surgery, the positive predictive value of diagnostic accuracy was 82.0% (males 91.2%, females 67.7%). Delaying surgery did not significantly increase the proportion of perforated appendices (22.0%), hospital stay, or frequency of postoperative complications (overall 49.6%). Hospital complications were significantly more common among patients with a perforated appendix. There was no significant difference in the complication rate between patients with or without appendicitis while in hospital, during the first 18 months after operation or 8 years after operation. At 18 months, 17 of 238 patients (7.1%) continued to experience their original pain. After 8 years the original pain was still present in 10 of 155 patients (6.5%). Continued pain was more likely in patients having undergone removal of a normal appendix (P < 0.001)