OBJECTIVE: There is now strong evidence that screening for colorectal cancer with fecal occult blood tests (FOBTs) is effective in reducing the incidence and mortality of this disease. Various FOBTs are now available with a wide range of evidence supporting their use. The purpose of this study was to review published data on the performance of these FOBTs to provide recommendations for their effective use in screening. METHODS: A joint committee representing the World Health Organization and the World Organization for Digestive Endoscopy was established for this study. A process was designed that would search the literature systematically for evidence of FOBT performance. Criteria for including studies in this paper were established based on study design, cohort size, and performance variables reported. RESULTS: Of the guaiac tests, Hemoccult SENSA had the highest sensitivity for cancer and adenomas but a high test positivity. It had a better readability than the older Hemoccult II test. Immunochemical tests, HemeSelect, FlexSure OBT, and Immudia Hem Sp have acceptable performance characteristics and are easier for participants to use but are more expensive. These tests have been well studied in large cohorts, but only Immudia Hem Sp is commercially available. CONCLUSIONS: At present, there is no extensively studied FOBT that fulfills the needs for all target populations worldwide. Choice of FOBT should take into account population dietary compliance and colonoscopy resources: The more sensitive newer tests should be used if dietary compliance is good (in the case of guaiac tests) and colonoscopy resources are adequate for diagnostic workup of people who test positive. Immunochemical tests remove the difficulties created by diet and drug restrictions and are more amenable to standardized development and quality control.