In analyzing mortality data from 5,800 cases of appendicitis, the cases were grouped according to the pathological stage of the disease at the time of initial treatment. The mortality rates ranged from 0.1% (appendix inflamed but not gangrenous) to 13.1% (appendiceal abscess not treated initially by appendectomy). The deaths in recent years were caused by nonseptic complications as much as by peritonitis or metastatic abscesses. In 4 out of 5 cases the preoperative diagnosis was correct. In 1 out of 6 cases the appendix was found to be perforated. No trend towards earlier referral for surgery was noted over a 20-year period. Further reductions in mortality depend on improved general support of the patient and on control of nonseptic complications.