The association between colonic neoplasms and gastric polyps (GP) was evaluated. Two hundred and sixty patients with known colonic neoplasms undergoing gastroduodenoscopy for abdominal symptoms, with or without anemia, were evaluated for the occurrence of synchronous GP. There were 100 patients with 1-4 colonic adenomas, 80 patients with multiple (5 or more) colonic adenomas and 80 patients with colorectal cancer. One hundred patients free from colonic neoplasms, investigated for abdominal pain or anemia, served as controls. The overall occurrence of GP in patients with colonic neoplasms was 18.8% compared to 1% in the control group. Hyperplastic GP were found in 4, 22.5, 18.7 and 1% of these patients, respectively, while gastric adenomas occurred in 2, 3.7, 3.5 and 0% respectively. Patients with colorectal cancer or multiple colonic adenomas had significant more GP than patients with 0-4 colonic adenomas. It is suggested that gastroduodenoscopic evaluation should be performed in patients with colorectal cancer or with 5 or more colonic adenomas.