BACKGROUND: Colorectal cancer is the second leading cause of cancer-related death in the United States, yet recommended screenings are not delivered to most people. This assessment of colorectal cancer screening's value to the U.S. population is part of the update to a 2001 ranking of recommended clinical preventive services found in the accompanying article. This article describes the burden of disease prevented and cost-effectiveness as a result of offering patients a choice of colorectal cancer screening tools. METHODS: Methods used were designed to ensure consistent estimates across many services and are described in more detail in the companion articles. In a secondary analysis, the authors also estimated the impact of increasing offers for colorectal cancer screening above current levels among the current cross-section of adults aged 50 and older. RESULTS: If a birth cohort of 4 million were offered screening at recommended intervals, 31,500 deaths would be prevented and 338,000 years of life would be gained over the lifetime of the birth cohort. In the current cross-section of people aged 50 and older, 18,800 deaths could be prevented each year by offering all people in this group screening at recommended intervals. Only 58% of these deaths are currently being prevented. In year 2000 dollars, the cost effectiveness of offering patients aged 50 and older a choice of colorectal cancer screening options is $11,900 per year of life gained. CONCLUSIONS: Colorectal cancer screening is a high-impact, cost-effective service used by less than half of persons aged 50 and older.