Mucosal lymphoid follicles reportedly do not occur in normal gastric mucosa or are rare. Detection of many primary and occasional secondary lymphoid follicles in the otherwise normal mucosa of a patient with multiple gastric sarcomas prompted study of the lesions of 84 patients--30 males and 54 females--and 2 fetuses. The conditions in the group were intramural tumors (27 cases), intramucosal lesions (16 cases), and putatively normal mucosa (43 cases). Overall, 229 sections totaling 567 cm of mucosa were examined and the lymphoid follicles counted. Follicles were found in 174 sections of 76 patients (88%) and in all categories examined except the fetuses. There were 773 follicles in fundal mucosa and 43 in antral mucosa (average, 1 follicle/7 mm of fundal mucosa and 1 follicle/21 mm of antral mucosa). The follicles were most frequent in the patients with multiple stromal sarcomas (1 follicle/8 mm of mucosa) and least frequent in pediatric patients.