On September 23, 2010, the American Board of Medical Specialties (ABMS) approved emergency medical services (EMS) as a subspecialty of emergency medicine. As a result, the American Board of Emergency Medicine (ABEM) is planning to award the first certificates in EMS medicine in the fall of 2013. The purpose of subspecialty certification in EMS, as defined by ABEM, is to standardize physician training and qualifications for EMS practice, to improve patient safety and enhance the quality of emergency medical care provided to patients in the prehospital environment, and to facilitate integration of prehospital patient treatment into the continuum of patient care. In February 2011, ABEM established the EMS Examination Task Force to develop the Core Content of EMS Medicine (Core Content) that would be used to define the subspecialty and from which questions would be written for the examinations, to develop a blueprint for the examinations, and to develop a bank of test questions for use on the examinations. The Core Content defines the training parameters, resources, and knowledge of the treatment of prehospital patients necessary to practice EMS medicine. Additionally, it is intended to inform fellowship directors and candidates for certification of the full range of content that might appear on the examinations. This article describes the development of the Core Content and presents the Core Content in its entirety.