Medical physicists and engineers, working with radiologists and technologists, have made significant contributions in the design of mammographic x-ray units and image receptors, as well as in the development of methods for evaluating mammographic image quality and procedures for quality control. More accurate methods of measuring radiation exposure in the energy range of mammography and more relevant calculations of radiation dose to breast tissue at risk have also been realized. This article will discuss some of the major contributions made by medical physicists for the benefit of mammography. Contributions of radiologists in mammography have been published elsewhere [Bassett, Gold, and Kimme-Smith (1994)]. All contributions cited in this article are based on referenced publications and citations in the following: Medical Physics; Radiology; NCRP Report No. 85; Quality Determinants in Mammography; AAPM Report No. 29; Reduced Dose Mammography, W. W. Logan and E. P. Muntz (editors); RSNA Categorical Course: Technical Aspects of Breast Imaging, A. Haus and M. Yaffe (editors); Film Processing in Medical Imaging, A. G. Haus (editor); Screen-Film Mammography: Imaging Considerations in Medical Physics, G. T. Barnes and G. Donald Frey (editors). The article is divided into six sections: (1) x-ray equipment and receptor development, (2) image quality, (3) radiation dose, (4) phantoms, (5) quality assurance, (6) digital mammography, and (7) reports and committees.