The solitary gastric erosion of Dieulafoy is rarely recognized but is not an uncommon cause of massive upper gastrointestinal hemorrhage. The English literature has only recently described this lesson in vivo. Its etiology and pathogenesis has remained poorly defined since first described in 1896. We have recently studied a series of nine cases (the largest English literature series), five of which were recognized and diagnosed at operation. Multiple tissue staining techniques were used to study the biopsy specimens for "clues" as to the pathogenesis of this lesion to be a vascular dysplasia that is associated with chronic gastritis and that thrombosis and necrosis of the abnormally tortuous submucosal artery occurs before perforation and exigent bleeding. The total lack of inflammatory reaction at the base of the lesion precludes a diagnosis of "ulceratio simplex" as originally described.