The subject of my remarks to-day, appendicular fistula, is such a common sequel to operations for acute appendicitis and is of such great importance to the future welfare of the patient, that I can not too strongly invite your attention to this subject. It is one of the most important sequels to appendicitis operations, for several reasons: on account of its effect on the constitution, the organs it may involve, and the danger in which it may place the patient in regard to future health. That many fistulæ may be avoided, if earlier operative measures were instituted, can not be questioned. This apparently is a very strong presentation to make, but I shall endeavor to show later in the discussion my reasons for making such a statement. I shall discuss this subject by taking up the varieties, the causes and dangers, the means of prevention, and the treatment.