Objectives: The role of vascular ectasia (VE) as a cause of bleeding in the upper GI tract (UGIB) in patients with chronic renal failure (CRF) is controversial. We evaluated the prevalence VE as a cause of UGIB in patients with CRF and examined factors associated with its presence. Methods: Over a 50-month period (from August 1, 1990, to September 30, 1994) all patients with UGIB evaluated by our gastroenterology consultative service at a large inner city hospital were prospectively identified. CRF was defined as a serum creatinine concentration ≤2 mg/dl for the 6 months before and after the bleeding episode. Endoscopy was performed in all patients, usually within 48 h of admission. VE was considered causative if the typical endoscopic features were observed in the absence of other potential bleeding sources. Results: Of the 727 patients with UGIB undergoing endoscopy, 60 (8%) had CRF. The mean age of these patients was 61 ± 15 yr, and the mean serum creatinine concentration was 5.6 mg/dl (range, 2-29.4 mg/dl). Hypertension and diabetes mellitus were the most common causes of renal failure. Gastric ulcer (37%) and duodenal (23%) ulcer were the most frequently identified causes of UGIB, followed by VE in eight patients (13%). VE was significantly more common in patients with CRF (13 vs 1.3%, p < 0.01). The prevalence of VE as a cause of UGIB was related to duration of renal failure (p = 0.004) and need for hemodialysis (p < 0.0001). VE was also the most frequent cause of recurrent bleeding in these patients. Conclusions: The most common cause of UGIB in patients with CRF is peptic ulcer disease. VE is more frequent in patients with CRF than in those with normal renal function, and its prevalence seems to be related to the duration and severity of renal disease.