BACKGROUND: Standardized reporting systems for diagnostic and screening tests facilitate quality improvement programs and clear communication among health care providers. Although colonoscopy is commonly used for screening, diagnosis, and therapy, no standardized reporting system for this procedure currently exists. The Quality Assurance Task Group of the National Colorectal Cancer Roundtable developed a reporting and data system for colonoscopy based on continuous quality improvement indicators. DESIGN: The Task Group systematically reviewed quality indicators recommended by the Multi-Society Task Force on Colorectal Cancer and developed consensus-based terminology for reporting and data systems to capture these data elements. The Task Group included experts in several disciplines: gastroenterology, primary care, diagnostic imaging, and health care delivery. RESULTS AND CONCLUSIONS: The standardized colonoscopy reporting and data system provides a tool that can be used for efforts in continuous quality improvement within and across practices that use colonoscopy.