Although the Zenker type of diverticulum is often considered to arise primarily in the esophagus, it is more correct to associate it with the lower portion of the pharynx. As a compromise it is sometimes described as a pharyngoesophageal diverticulum. Because of the fact that this type of diverticulum almost always produces difficulty in swallowing, it is recognized during life much more commonly than diverticula that are of true esophageal origin. Esophageal diverticula are of much commoner occurrence than diverticula which arise from the pharynx, but because esophageal diverticula are usually of the so-called traction type, the apex of the sacculation points upward and rarely becomes of sufficient size to produce any symptoms referable to the esophagus. When these diverticula are found, it is almost always incidentally, at necropsy. Occasionally infection of the sac may occur, with perforation into a bronchus or into the mediastinum, resulting in the formation of