The medical audit of a mammography practice is a recognized method for evaluating mammography and the accuracy of mammographic interpretation [1-4]. As such, portions of the audit will become integral to the quality assurance activities of every mammography practice under the Mammography Quality Standards Act (MQSA) of 1992, administered by the Food and Drug Administration (FDA). The FDA Interim Rules, which became effective October 1, 1994, state that "each facility shall establish a system for reviewing outcome data from all mammography performed, including follow-up on the disposition of positive mammograms and correlation of surgical biopsy results with mammogram reports" [5]. It is expected that the proposed final rules, due to be released for public comment in 1995, will require collection of additional data for medical audits (public meeting of the National Mammography Advisory Committee, May 3, 1994). Although most mammography practices are now collecting clinical outcomes data on abnormal mammographic examinations, very few have established an organized and deliberate system of data collection necessary for a more complete mammography audit [6]. A detailed discussion of and recommendations for such an audit were recently published as part of the Quality Determinants of Mammography Guideline by the Agency for Healthcare Policy and Research (AHCPR) [7]. As members and consultants on the multidisciplinary panel that produced the guideline, we offer the following review of the various elements, definitions, and processes of the mammography audit. This is intended as a primer for all radiologists who will be performing some of the same audit activities for the MQSA.