The distribution of Campylobacter pylori, its prevalence, and its relationship to gastritis and urease activity have been studied in 54 postmortem stomachs. Infection was confirmed by finding C. pylori in a Gram-stained smear of gastric mucus harvested from the entire stomach. Eight tissue specimens were obtained from predetermined sites from each stomach and examined for histologic gastritis and urease activity. Thirty-seven per cent of stomachs were infected, and of these 80% had widespread histologic gastritis. The detection of urease activity provided information on the distribution of the organism and had a high correlation with histologic gastritis. The organism is capable of infecting any area of the stomach. Infection is common and is more prevalent in Polynesian subjects (60%) than in Caucasians (19%).