This article discusses the background, goals, criteria, current results, impact, and future directions of the American College of Radiology's (ACR's) Mammography Accreditation Program. To date, approximately one half of the mammographic units in the United States have voluntarily applied for accreditation through the ACR program, with approximately one quarter of the units in the United States now accredited. Application rates have increased steadily since the start of the program in August 1987. The equipment performance criteria and professional criteria defined and employed in the ACR Mammography Accreditation Program have been adopted as standards for the performance of screening mammography by the ACR and have served as a basis for quality assurance standards in state and federal legislation on mammography.