The amount of gastrin-like immunostaining in gastrin (G) cells of the antral mucosa was quantified using a computer-assisted method of measuring immunoreaction product. Biopsies from 25 patients without Heliobacter-like organisms and 60 patients with varying degrees of infection were immunostained for gastrin. Twenty-five G cells from each patient were measured both subjectively and by image analysis. Gastrin-like immunoreactivity was found to be significantly increased in the presence of Heliobacter-like organisms.