Pyloric deformation from peptic disease. Radiographic evidence for incompetence rather than obstruction. We have used double-contrast radiographic techniques to clarify what changes in the configuration and movements of the gastroduodenal junction result when peptic lesions involve the distal gastric segment between the proximal (PPL) and the distal pyloric muscle loop (DPL). Among 50 cases of pyloric ulceration diagnosed during a four-year study period, 18 cases fulfilled all study criteria. Ulcers maintained a consistent location with regard to the muscular structures of the pylorus, and by affecting these structures, led to many strange deformations of the gastric outlet including permanent pseudodiverticula and reversal of pyloric angulation. The most common site for peptic lesions in the pyloric segment was the protuberance of the lesser curvature called the pyloric torus; many torus lesions extended into and destroyed the DPL. This led to widening of the gastric outlet and radiographic evidence of increased duodenogastric reflux. Pyloric closure was further impaired in this setting because the mucosa no longer prolapsed into the gastric outlet and did not occlude the pyloric lumen as it normally does. Less common lesions involved the greater curvature and the PPL. In one patient, scarring of the PPL led to an antral web and gastric hyperperistalsis. This was the only patient who required operation for chronic gastric outlet obstruction. One-third of the 18 patients had reflux esophagitis in addition to peptic pyloric disease. In most patients without additional ulcerogenic risk factors, treatment with antisecretory agents led to the healing of ulcer craters. We conclude that the morphologic and functional changes of the gastric outlet caused by peptic lesions depend, in part, on the effect the ulcer has on the underlying pyloric musculature. 