Objective. Cytomegalovirus (CMV) infection is known to cause ulcerations, erosion and mucosal haemorrhage in the gastrointestinal tract. The aim of this study was to report the CMV findings in the gastroduodenal mucosa of kidney transplantation patients and immunocompetent controls. Material and methods. Forty-six kidney transplant patients with upper gastrointestinal symptoms and 43 immunocompetent,dyspeptic patients (controls) prospectively underwent oesophagogastroduodenoscopies (OEGDs), with biopsies from the duodenum and stomach. CMV was demonstrated by immunohistochemistry, both in frozen sections using a monoclonal antibody against CMV-specific antigens (pp65 matrix protein) and in paraffin sections by means of a monoclonal antibody against the delayed early protein (p52). Results. CMV was detected in the gastric mucosa in 30%of the kidney transplant patients and in 9%of the controls (p < 0.05) and in the duodenal mucosa in 70%and 35%, respectively (p < 0.01). The total frequency of CMV findings was similar in patients who underwent OEGDs < 1 year and > 1 year after transplantation. CMV inclusions were found only in transplantation patients < 1 year after transplantation (n = 9). CMV findings, especially inclusions, in the gastric biopsies were associated with nausea and upper gastric pain. Histopathological findings in CMV-positive samples were non-specific, focal inflammation in haematoxylin-eosin-stained preparations, while CMV p52 staining showed inclusions in either the epithelial or endothelial cells. Conclusions. CMV could be detected in the gastroduodenalmucosa in 74%of kidney transplantation patients and in 40%of immunocompetent controls (p < 0.01). CMV diagnostics are always recommended when gastroduodenal biopsies of kidney transplantation patients are performed. Objective of this study was to report the CMV findings in the gastroduodenal mucosa of kidney transplantation patients and immunocompetent controls. Material and methods. Forty -six kidney transplant patients with upper gastrointestinal symptoms and 43 immunocompetent, dyspeptic patients (controls) prospectively underwent oesophagogastroduodenoscopies (OEGDs), with biopsies from the duodenum and stomach. CMV was demonstrated by immunohistochemistry, both in frozen sections using a monoclonal antibody against CMV- specific antigens (pp65 matrix protein) and in paraffin sections by means of a monoclonal antibody against the delayed early protein (p52). Results. CMV was detected in the gastric mucosa in 30% of the kidney transplant patients and in 9% of the controls (p <0.05) and in the duodenal mucosa in 70% and 35%, respectively (p <0.01). The total frequenc CMV findings, especially inclusions, in the gastric biopsies (n = 9). CMV findings were particularly similar to those who underwent OEGDs <1 year and> 1 year after transplantation. were associated with nausea and upper gastric pain. Histopathological findings in CMV-positive samples were non-specific, focal inflammation in haematoxylin-eosin-stained preparations, while CMV p52 RINECTED in either the epithelial or endothelial cells. Conclusions. CMV could be detected in the gastroduodenal mucosa in 74% of kidney transplantation patients and in 40% of immunocompetent controls (p <0.01). CMV diagnostics are always recommended when gastroduodenal biopsies of kidney transplantation patients are performed.