Breast radiography should be performed only with film-screen mammography or xeromammography. At least two views of each breast should be obtained, and for film-screen mammography, at least one of these should be the oblique view. Quality assurance is becoming a significant concern in breast cancer screening. The ACR Mammography Accreditation Program takes into account the qualifications of the personnel, the performance of the x-ray equipment, and a peer review of the final product: the diagnostic image. The mammographic signs of malignancy can be divided into primary, secondary, and indirect. The accuracy of mammography depends on several factors, but the greatest limitation is the density of the breast tissue. Very dense tissue makes detection of breast cancer difficult, and a negative mammogram should never deter one from a biopsy of a clinically suspect mass. New consensus guidelines for breast cancer screening were developed to bring uniformity to the recommendations of the American Cancer Society, the National Cancer Institute, and various professional medical societies. These new guidelines reflect the encouraging results from recent clinical trials, as well as some discouraging reports on breast self-examination and the baseline mammogram. The underutilization of screening mammography is a problem of significant concern to both private and public health agencies. Barriers to mammographic screening include lack of awareness of the benefits of screening, physicians' misconceptions about patient compliance, concerns about radiation risk and overdiagnosis, fear of mastectomy, a perception that a mammogram involves great discomfort, and relatively high cost. Nationwide educational programs are under way to counter misconceptions about mammography, and various strategies are evolving to overcome the other barriers. Sonography is a useful adjunct to mammography for cyst-solid differentiation, but mammography is the only imaging modality effective for the early detection of breast cancer.