Image quality is the cornerstone to the practice of high-quality mammography. To ensure high quality in the practice of mammography, the American College of Radiology has established a voluntary program for the accreditation of mammographic screening sites. Between August 15, 1987, and February 1, 1989, 647 mammography units completed the accreditation program. Data collected from those units are presented, demonstrating that broad ranges of image quality and dose currently exist among mammographic screening sites. Reasons are discussed for the wide ranges observed, and steps are proposed to narrow the ranges of image quality and dose in the practice of mammography.