Since the release of the Institute of Medicine's report on resident hours and patient safety, there have been calls for enhanced institutional oversight of duty hour limits and of efforts to enhance the quality and safety of care in teaching hospitals. The ACGME has established the Clinical Learning Environment Review (CLER) program as a key component of the Next Accreditation System with the aim to promote safety and quality of care by focusing on 6 areas important to the safety and quality of care in teaching hospitals and the care residents will provide in a lifetime of practice after completion of training. The 6 areas encompass engagement of residents in patient safety, quality improvement and care transitions, promoting appropriate resident supervision, duty hour oversight and fatigue management, and enhancing professionalism. Over the coming 18 months the ACGME will develop, test, and fully implement this new program by conducting visits to the nearly 400 clinical sites of sponsoring institutions with two or more specialty or subspecialty programs. These site visits will provide an understanding of how the learning environment for the 116 000 current residents and fellows addresses the 6 areas important to safety and quality of care, and will generate baseline data on the status of these activities in accredited institutions. We expect that over time the CLER program will serve as a new source of formative feedback for teaching institutions, and generate national data that will guide performance improvement for United States graduate medical education.