Primary adenocarcinoma of the appendix is divided into the cystic type and the colonic type, and more than 200 cases have been reported in Japan. But few of them were diagnosed preoperatively. A 73-year-old man with early primary adenocarcinoma of the appendix is reported in this paper. He had the chief complaint of abdominal distention and was suspected of having primary adenocarcinoma of the appendix preoperatively by colon fiberscopy. Ileocecal resection with lymphnode dissection was carried out. Pathologically, this patient was interesting in the that he had histological findings of both the cystic type and the colonic type. Additionally, 100 cases of primary adenocarcinoma of the appendix in Japan reported during the past 7 years were collected and analyzed as to sex, age, symptoms, preoperative diagnosis, depth of invasion, operation method and prognosis. Right hemicolectomy or ileocecal resection with lymphnode dissection should be carried out in all primary adenocarcinomas of the appendix.