AbstractTumor tissue samples from 25 patients with adenocarcinoma of the colon, twelve related samples of normal colons as well as five serum specimens from the same patients were analyzed for ferritin. The average ferritin content of the tumor tissue was 788 ng/mcp1with a range of 47–1,745 ng/mcp. The average ferritin content of normal colon mucosa was 115 ng/mcp with a range of 32–230 ng/mcp. Two specimens of metastatic colon cancer taken from the retroperitoneal space and liver, respectively, contained 3,867and 2,827 ng/mcp of ferritin. The ferritin content of the tumor tissue was higher than that of the normal colon in 8 of 9 patients who had specimens obtained from both sites. me amount of ferritin found in tumor tissue was independent of sex, age, and the site of the original tumor. This study shows that the ferritin content of colon neoplasms is elevated and indicates that the tumor tissue may be the direct source of elevated serum levels of ferritin previously observed in cancer patients.