Intussusception of the appendix into itself is rare, and only 2 cases have previously been reported. The purpose of this paper is to report another case and to discuss the pathologic picture and possible etiologic factors of this condition. Frazer (1943)1 stated that at the time of his report there had been about 100 cases of appendical intussusception of all types recorded in the literature. He added 7 more and reviewed 75 out of the 100 previously reported. This group included all three types of intussusception: (a) simple, i. e., into itself; (b) the appendix invaginating into the cecum, either partial or complete, and (c) compound, i. e., the appendix invaginating into the cecum and the cecum into the ascending colon. This paper deals with the simple type of intussusception and adds a third case of this kind. F. Whitrow (1930)2 presented the first case report. Her patient