Follicular gastritis (FG) is characterized by lymphoid follicle hyperplasia in the gastric mucosa. The aim of this prospective study was to determine the prevalence of FG in adults, their relation to Helicobacter pylori infection, and their histological and endoscopic features. Of 445 patients (379 men, 66 women), 36.4 years old (range: 18-86), FG was detected in 63 patients (14.2%). This was highly significantly associated with H. pylori infection: 49/138 infected patients (35.5%) versus 14/307 non infected patients (4.6%) (P < 0.001). None of the histological features of the antral mucosa were correlated with FG. The prevalence of FG in patients less than 20 years old (in 45.4%) and between 20 and 40 years (in 41.3%) was higher than in patients aged from 40 to 60 years (in 33%) and older than 60 years (in 23%) (no significant difference). No one endoscopic feature of the gastric mucosa was predictive of the presence of FG. We conclude that FG is highly correlated with H. pylori infection and represents a local immune response to bacterial antigens. Their occurrence is probably multifactorial and related to age, duration of infection, bacterial strains, host immune status.