The etiology, prognosis, and optimal management of primary gastric carcinoids remain controversial. Records of 36 consecutive patients with gastric carcinoid (15 men) were reviewed retrospectively between 1975 and 1990. Follow-up was complete in 97% of cases. Mean age at diagnosis was 58.4 years (range 24-82 years). The clinical presentations included anemia (72%), pain (69%), and carcinoid syndrome (11%). Associated autoimmune and endocrine abnormalities were common and included atrophic gastritis (67%), pernicious anemia (58%), hypothyroidism (39%), diabetes (19%), Addison's disease (6%), and hyperparathyroidism (6%). Lesions were nonantral in 78%, involving only the corpus in 42%, the fundus in 28%, and only the antrum in 8%; 42% were multiple. Urinary 5-hydroxyindoleacetic acid (5-HIAA) and serum gastrin levels were elevated in 17% and 50% of those tested, respectively. Histologic examination revealed that 28% of lesions were > or = 2 cm, and 33% had liver metastases on presentation or developed them during follow-up. Eight patients (22%) died of tumor with a median survival of 39 months. The presence of metastases, atypical histology, serosal involvement, and size > 2 cm were adverse prognostic factors. In patients without hypergastrinemia (n = 6), 66% developed metastases, 60% had elevated 5-HIAA, and 50% died of carcinoid tumor. In sharp contrast, those patients with hypergastrinemia and "typical" gastric carcinoids (n = 15), metastases and death did not occur (p < 0.003 and p < 0.005, respectively, compared with eugastrinemic patients).(ABSTRACT TRUNCATED AT 250 WORDS)