During a 5-year period, we examined by endoscopy or surgery 2634 stomachs: 2536 (group A) were free of lesions commonly recognized as mucosal "polyps"; 74 (group B) exhibited hyperplastic polyps; and 24 (group C) were found with neoplastic (adenomatous) polyps. Carcinomas were present in 318 (12.5%) of specimens in group A, compared with 10 (13.5%) in group B and 20 (83.3%) in group C. In the third group, 14 carcinomas were encountered within polyps, and 4 carcinomas occurred separately. The frequency of cancer associated with neoplastic polyps was relatively low (1 of 3) in patients younger than 50 years, but significantly high (19 of 21) in older patients. This series confirms the prevailing concept that patients harboring gastric adenomatous polyps are at distinct risk of gastric carcinoma, a risk that sharply rises with age. We conclude that patients found with gastric adenomatous polyps should be subject to careful and continued surveillance to ensure that supervening carcinoma be detected at the earliest possible phase.