PURPOSE: Diverticular disease of the cecum and ascending colon is a relatively uncommon disease and there are some difficulties in the accurate preoperative diagnosis and the proper surgical treatment. This study is aimed to determine what is the proper procedure during the emergency operation of right colon diverticulitis. METHODS: This study is a retrospective clinical analysis of 86 cases of the right colon diverticulitis from January 1992 to December 1999. RESULTS: 1) The incidence of right colon diverticulitis (RCD) was 2.1% of that of appendicitis and the RCD to sigmoid colon diverticulitis ratio was 9.6:1.2) The highest incidence was noted at the fourth decades and average age was 37 years. Male to female ratio was 1.9:1. 3) Most patients (73 cases, 85%) had right lower quadrant abdominal pain. 4) The duration of symptom was less than 3 days in 54 cases (63%). 5) The preoperative confirmation by radiologic work-up was not decisive, but barium enema might be more accurate than other studies and CT was more accurate method than ultrasound. 6) The correct preoperative diagnosis was made only in 13 cases (15%) and the remaining misdiagnoses were appendicitis with or without complications in 72 cases (83%). 7) Operative procedures varied markedly according to multiplicity, extent of inflammation and complications; diverticulectomy and appendectomy in 48 cases (56%), ileocecectomy in 15 cases (17%) and right hemicolectomy in 11 cases (13%). 8) The most commom postoperative complication was wound infection. 9) Among the 30 cases who took diverticulectomy or diverticulectomy and appendectomy, remained diverticulums were found in 14 cases (47%), especially 11 cases (37%) on the right colon. And so multiplicity of right colon reached about 37%. CONCLUSIONS: The authors suggest that one should suspect RCD in fourth decade patients with right lower quadrant pain for more than 3 days with unusual clinical findings. Barium enema can be used because of the high accuracy rate but CT is a safe tool in complicated or urgent situation. The operative modalities should be selected on the extent of the disease and it is sufficient to treat a single diverticulitis with diverticulectomy or diverticulectomy and appendectomy but right hemicolectomy should be recommanded in the suspicious multiplicity or malignancy.