Fecal occult blood testing by immunochemical hemagglutination has been shown to be superior to the Hemoccult test, both in sensitivity and in specificity. The test has been widely used as a tool for population screening in Japan, but there has been no study to evaluate the efficacy of screening using this test. A case-control study to evaluate the screening was conducted in study areas where no previous and no other concomitant colorectal cancer screening had been performed. Case series in the study were 193 cases who died of colorectal cancer. Three controls were selected randomly from the list of individuals who were alive at the time of diagnosis of the corresponding case and had been living in the same area as the case, matched by gender and by age. Odds ratios (OR) of dying of colorectal cancer for those screened within 1, 2 and 3 years of case diagnosis vs. those not screened were 0.40 [95% confidence interval (CI) 0.17-0.92], 0.41 (95% CI 0.20-0.82), and 0.48 (95% CI 0.25-0.92), respectively. OR increased towards 1.0 as the duration during which screening histories were compared was extended, and showed similar tendencies when analyzed by number of years since the most recent screening history. These results suggest that colorectal cancer screening by the immunochemical fecal occult blood test would reduce mortality from colorectal cancer.