The purpose of routine screening mammography is to detect unsuspected cancer that has the potential to be cured. Abnormalities detected on the screening examination often necessitate additional radiologic workup before a definitive result or diagnosis can be given. This workup (diagnostic mammography) may include specialized views, such as spot compression to evaluate the margins of a nodule, or magnification views to determine the features of microcalcifications. Additional evaluation with mammographic views, breast ultrasound, and, at times, interventional procedures such as fine needle aspiration or core biopsy are performed to complete the radiologic evaluation of a patient with an abnormal mammogram. Signs of malignancy include nodules (most often poorly defined), microcalcifications, and, less commonly, areas of architectural distortion, asymmetry, or focal ductal dilatation. A comprehensive approach to breast imaging will help to potentiate the early detection of subtle malignancies and avoid the performance of some biopsies for benign lesions.