Phenol red dye spraying endoscopy, in addition to a biopsy study, was employed for the determination of Helicobacter pylori distribution on the gastric mucosa of 108 patients with no gross gastric findings. The sensitivity of this method was 100%, and its specificity was 84.6%. In patients with a C0 pattern of the fundic-pyloric (F-P) border, the H. pylori-positive rate was only 21%, but this increased with the spread of atrophic mucosa, to approximately 90%. However, in patients with an O3 pattern, H. pylori could not be found. In addition, in 24 (80.0%) of 30 patients with no glandular atrophy, this organism was not found, while, in contrast, the organism was demonstrated in 54 (85.8%) of 63 patients with a slight degree of glandular atrophy. In patients with severe mucosal atrophy accompanying intestinal metaplasia, however, the organism was not found. One-half of the patients examined were followed up, using this technique. In those who were H. pylori-negative, glandular atrophy remained unchanged, while advanced glandular atrophy was seen in 10 (28.6%) of 35 H. pylori-positive patients. A cephalad shift of the F-P border was observed in 20 (57.1%) of these 35 H. pylori-positive patients, while in those who were negative, the F-P border remained unchanged, with one exception.