Medical directors of cardiac rehabilitation/secondary prevention (CR/SP) programs are responsible for the safe and effective delivery of high-quality CR/SP services to eligible patients. Yet, the training and resources for CR/SP medical directors are limited. As a result, there appears to be considerable variability throughout CR/SP programs in the United States in the roles, responsibilities, and engagement of CR/SP medical directors. Since the publication of the 2005 scientific statement from the American Heart Association and American Association of Cardiovascular and Pulmonary Rehabilitation regarding medical director responsibilities for outpatient CR/SP programs, significant changes have occurred. This statement updates the responsibilities of CR/SP medical directors, in view of changes in federal legislation and regulations and changes in health care delivery and clinical practice that impact the roles and responsibilities of CR/SP medical directors. © 2012 American Heart Association, Inc.