Biopsy specimens from the gastric antral mucosa of 194 patients with upper gastrointestinal symptoms were studied with the Warthin-Starry silver stain to demonstrate the presence of Campylobacter Pylori (CP). Of these patients, 44 had peptic ulcer visible on endoscopic investigation. Spiral bacteria were detected in 70 out of 75 specimens with histologically active gastritis (93%), in 34 of 54 specimens with inactive form of gastritis (63%) and in 26 of 65 specimens without morphological changes (40%). Of 44 patients found to have gastric or duodenal ulcers, 33 also had bacteria. No significant differences between patients with endoscopically visible peptic ulcer and those without ulcer were seen. Our results indicate a close relationship between the active form of chronic gastritis and Campylobacter; however they do not show a definite association with peptic ulcer.