Upper gastrointestinal (UGI) symptoms are common in uremic patients, and higher serum levels of urea have been suggested to be related to Helicobacter pylori (HP) colonization and UGI mucosal inflammation. To compare HP infection and UGI endoscopic findings between uremic patients, renal transplantation recipients (Tx) and controls. A total number of 474 subjects (71chronic renal failure (CRF), 73 hemodialysis (HD), 25 Tx and 305 controls) from Baqyiatallah Hospital, Tehran, Iran were recruited between April 2002 and March 2004 for evaluation of dyspepsia, excluding Those receiving any HP-eradication therapy. All subjects were examined for any changes in their esophagus, stomach and duodenum mucosa and infection with HP using a fiber optic endoscope and color reagent in a 24-hour period on two distinct tissue samples of the anthral region. Four groups of subjects (mean±2se age 45±1.6 years, 62.9% male) were studied. Duodenal ulcer in the uremic patients (CRF: 16.1%; HD: 13.7%) was more common than that in the Tx subjects (8%) and controls (6.5%); P=0.038. Erosive gastritis and duodenal bulb deformity were also more common in the uremic subjects (CRF: 23.9%, 36.9%; HD: 30.1%, 20.5%, respectively) than those in the other subjects (Tx subjects: 16%, 8% and controls: 8.2, 0% respectively); P<0.001. HP infection was found to be higher in the uremic patients (CRF: 66.2%; HD: 63%) than that in the Tx subjects (40%) and controls (34.8%); P<0.001. Higher rates of gastric and duodenal mucosal lesions and HP infection in the uremic patients in comparison with the subjects with normal renal function may have resulted from higher serum levels of urea, anemia and fluctuations in the gastric blood supply in the CRF and HD patients. However, more tenable evidence from controlled trials is required for the eradication of HP in all uremic patients and Tx candidates.