After the initial report of Marshall and Warren, several publications have also demonstrated the presence of pyloric campylobacter in an elevated percentage of cases of chronic gastritis and peptic ulcer. We present our experience studying 672 patients examined by esophagogastroduodenoscopy after referral to clinical because of upper gastrointestinal symptoms. We used an Olympus GIF-K2 panendoscope taking two biopsies from the gastric antrum. Specimens were stained with hematoxilin-eosin and silver. In our experience these methods have given us the best results in detecting this bacteria. Diagnosis of gastric and duodenal ulcer was made by endoscopic criteria and chronic gastritis diagnosed by histology. Chronic gastritis was categorized into active and inactive based in the invasion of polymorphonuclear into mucosa. We have also quantitated damage of the mucin producing cells as well as the degree of bacterial colonization. We have found pyloric campylobacter in 91.8% of patients suffering from chronic active gastritis, 72.7% of patients with diagnosis of gastric ulcer and 84.2% of cases of duodenal ulcer. Our results agree with the ones reported by other authors. We conclude that pyloric campylobacter is not an opportunist microorganism within the stomach because it produces inflammatory changes as well as damage of the mucin producing cells. Its presence may play some role in the etiology of gastritis and peptic ulcer disease.