Two thousand four hundred and forty workers from 2 plants were enrolled in a mass survey for colorectal cancer using a single immunological fecal occult blood test as screening. The occult blood test was positive in 71 (4.0%) out of 1,759 subjects in whom the test was conducted. A further investigation, including total colonoscopy or barium enema, was performed on 52 (73.2%) of the 71. Colon cancer was detected in 5 cases: 1 with advanced cancer and 4 with early cancer (cancer in the adenoma). The advanced cancer was successfully resected by surgery and the early cancers were removed by endoscopic polypectomy. Adenomas were found in 21 cases, 11 of which were polypectomized. From these results, it can be seen that a survey for colorectal cancer at the workplace is important, and by expanding the number of subjects for the survey in the workplace we can expect more and earlier detections of colorectal cancer.