Records of the 30 cases of gastric carcinoid at the Mayo Clinic showed that the gastric mucosa was normal, hyperplastic, or atrophic (nonantral) in 12, 2, or 16 patients, respectively. In the atrophic group, the tumors were in the gastric body and fundus; small, polypoid, and multicentric; and associated with fundal argyrophil cell hyperplasia. In immunocytochemical studies, minor tumor cell populations stained positively for 5-hydroxytryptamine, gastrin, and somatostatin in 1 case and for 5-hydroxytryptamine in 3 others. Metastasis occurred in 3 patients. Twelve patients had pernicious anemia. Parietal cell or intrinsic factor antibodies or both were present in all 12 patients tested. Each of the 7 patients with an intact antrum had massive hypergastrinemia. No common HLA-A, -B, or -DR antigen pattern was detected among the 10 patients tested. The results suggest that nonantral gastric atrophy predisposes to gastric carcinoid as well as to gastric carcinoma.