In 236 out of 11,150 (1.8%) patients operated upon for acute appendicitis some other acute surgical and gynecological diseases were revealed. In this group of patients the vermiform process either seemed to be unchanged or its changes were considered to be secondary ones (reaction to an inflammation in adjacent organs). Histological study of vermiform processes proved the abscence of inflammatory alterations only in 35 cases. In the rest of patients either chronic or acute inflammatory process was found. The conclusion has been drawn that in case when diagnosis of acute appendicitis is not confirmed during operation, appendectomy does not produce any unfavourable effect upon the postoperative clinical course and outcome of the main disease and should be considered as a compulsory element of a surgical intervention.