To investigate the value of Papanicolaou-stained endoscopic brush samples in the diagnosis of Campylobacter pylori infection of the upper gastrointestinal tract, 138 brush and biopsy samples from the esophagus, stomach, and duodenum, taken concomitantly, were reviewed retrospectively. In 35 cases, Campylobacter-like organisms (CLOs) were found in both cytology and biopsy samples. In 15 cases, CLOs were seen in biopsy material only, and in 8 cases, CLOs were found in cytology material only. CLOs were found in 49% of the gastric specimens and 33% of the Barrett's esophagus specimens by histologic or cytologic examination or by both methods. CLOs were found by at least one method in 64% of the gastric samples with active gastritis 40% with borderline gastritis, 15% without gastritis, and in 64% with adenocarcinoma. Cytologic examination of endoscopic brush samples is a valuable technique for the diagnosis of gastric Campylobacter infections and can be performed easily in cytopathology laboratories.