Serum concentration of gastrin determined by radioimmunoassay in 90 consecutive patients who underwent colonoscopy, and serum levels of gastrin in patients with colorectal neoplasia and controls were compared. Based on clinical history, findings of colonoscopy, and pathologic examinations of biopsies, 80 patients were considered eligible for the study. Serum levels of gastrin in 36 controls were 54.1 +/- 13.1 pg/ml and did not differ from serum levels of gastrin in 44 patients with colorectal neoplasia. There was also no significant difference in serum levels of gastrin among 28 patients with adenomas and 16 patients with carcinoma. The present study disclosed that carcinogenesis of the colon and rectum was not associated with hypergastrinemia.