HISTORICAL DATA In 1764 Ludlow1 observed "preternatural pockets" in the esophagus at autopsy. In 1816 Bell2 published in his volume of "Surgical Observations" a paper entitled "A Praeternatural Bag, Formed by the Membrane of the Pharynx." CLASSIFICATION In 1877, Zenker and von Ziemssen3 were the first to classify diverticula of the esophagus into traction and pulsion types. They also made a study of the literature (23 cases) and added 5 of their own, in which autopsy was performed. In 1922, Bensaude, Grégoire and Guénaux4 made a new classification of esophageal diverticula—those of the esophagus are distinguished from pharyngoesophageal diverticula. Traction Diverticula. —In 1840, Rokitansky5 first correctly described traction diverticula. Etiology. —In 1816, Bell2 described the condition as due to distention of the pharynx from ineffectual attempts to swallow, with resultant protrusion of the inner coats of the pharynx through hypertrophied bundles of the inferior