An evaluation was made of a bioptic material (21,916 appendices recovered from 1965 to 1974), in order to disclose relationships of the incidence of Enterobius vermicularis and the origin of appendicitis. A separate evaluation was made of a set of appendectomies (10,619 cases--from 1961 to 1970) for the purpose of detecting changes in pin worm-infested appendices by means of histological methods (683 cases). E. vermicularis was found in 6.03% of appendices. Included in our histological examination was a search for granulomas and eosinophile infiltrations. The former occurred in 1.14% of pin worm-infested appendices, the later in 1.74% and in 0.19%, or 2.18% in pin worm non-infested appendices. The results indicated a statistically highly significant difference in the incidence of granulomas. The incidence of granulomas in the appendix was increased in the present of pin worms in the appendix, and seemed also to be responsible for further pathological changes in it.