Angiodysplasia of the stomach, the proximal part of the small intestine, or both was diagnosed in 30 patients by upper gastrointestinal (Gl) endoscopy over a 40-month period. This diagnosis represented 4% of 676 patients referred over the same time period for endoscopic examination of suspected upper Gl bleeding. Twenty-three patients (77%) had experienced at least one episode of overt bleeding (hematemesis or melena) prior to diagnosis. Multiple gastroduodenal angiodysplastic lesions were found in 19 (63%) of the patients, and additional colonic angiodysplasia was detected in six of 12 patients who also underwent colonoscopy. Renal insufficiency was significantly more prevalent in the patients with angiodysplasia than in a comparison group of similar age with upper Gl bleeding from other lesions (60% v 24%). We conclude that angiodysplasia, although uncommon, should be considered in the differential diagnosis of both occult and overt upper Gl bleeding. The lesion appears to be associated with renal insufficiency.