After 4 years of research, development of standards with measurable criteria, and field tests, a voluntary accreditation process for rotor- and fixed-wing air medical services was initiated in July 1990 by the Commission on Accreditation of Air Medical Services. The Commission is a nonprofit organization incorporated in the state of Pennsylvania. The primary purpose of the Commission is to provide a voluntary evaluation process to measure compliance with accreditation standards in order to improve the quality of patient care and safety of the air transport environment in the United States and Canada. Since the Commission became operational in October 1991, 18 air medical services have achieved full accreditation, and another 22 services are in the process of completing various stages of the application process.