OBJECTIVE This study was designed to evaluate the sensitivity of OC-Hemodia, a immunochemical fecal occult blood test (IFOBT) based on the technique of latex agglutination for early stage colorectal cancer and clinically significant adenomas. METHODS The study was conducted on 885 patients who underwent OC-Hemodia and a colonoscopy. RESULTS Colorectal cancers were detected in 23 patients (10 Dukes' A, eight Dukes' B, and five Dukes' C or D). Adenomas were detected in 459 patients (16 villous adenomas 433 tubular adenomas with mild or moderate dysplasia, and 10 with severe dysplasia). The sensitivity of OC-Hemodia was 90% for those with Dukes' A colon cancer and 100% for those with Dukes' B, C, or D colon cancer. It was 18.8% for those with villous changes, and 40% for those with severe dysplasia. CONCLUSIONS These results suggest that the IFOBT is not a reliable test for the screening of premalignant adenomas, although it is useful for detecting early stage colorectal cancers.