Uraemic patients frequently complain of gastrointestinal ailments. There are a lot of factors responsible for the occurrence of these symptoms. It is considered--among other things--that high level of urea in gastric juice and hypergastrinaemia contribute to the damage of stomach and duodenum mucosa. Does H. pylori infection also produce pathological changes within upper gastrointestinal tract in these patients? The aim of the study was to determine the prevalence of H. pylori infection and macroscopic and microscopic estimation of oesophagus, stomach and duodenum mucosa in haemodialysis patients and renal transplant recipients. A total of 39 patients were taken under investigation: 27 among them were treated with haemodialyses and 12 were after kidney transplantation. In all patients upper gastrointestinal endoscopies were performed with collection of biopsy specimens for histological analysis and a urease test. Serological examinations were carried out in order to detect anti-CagA H. pylori antibody. In summary, we found that prevalence of H. pylori infection in uremic patients on chronic haemodialysis and renal transplant recipients was significantly lower than that in patients with normal renal function. This may be a consequence of medication and/or protection by a high urea concentration. Elevated blood urea seems to correlate with a high prevalence of gastroduodenal mucosal lesions.