The clinical and histologic material of 140 patients with gastric carcinoma resected more than 5 years previously was examined and 10 tumors with a previous diagnosis of adenocarcinoma showed atypical carcinoid differentiation. The clinical extent of tumors in this carcinoid group was similar to that of the ordinary gastric adenocarcinoma. The 5-year survival was 15% in patients with adenocarcinoma and 70% in those with carcinoid (P < 0.01 by χ2 test). These findings indicate the need to distinguish atypical carcinoids from ordinary gastric adenocarcinoma. The most commonly encountered histologic feature suggesting carcinoid, and leading to confirmatory histochemical studies, was found to be regular interlacing trabeculae of tumor and fibrovascular stroma.