Mammography and physical examination, usually employed as diagnostic tools, may be used to screen for early detection of breast cancer. A study of these modalities used to aggressively screen patients in Cincinnati and Milwaukee is presented and compared to more traditional methods of breast cancer detection and diagnosis as done in Louisville. For a similar-sized group over the same period, the rate of cancers detected in Louisville did not exceed that in Cincinnati-Milwaukee. Aggressive screening will not increase the overall number of detected cancers but will decrease the number of advanced cancers. Mammography as a screening device is not in itself a diagnostic tool, since its potential benefit is maximized only through the use of nondiagnostic, indirect radiographic criteria.