In a series of 2,522 mammograms, interpreted without benefit of clinical findings, 501 (96.7%) of 518 proved carcinomas were correctly diagnosed, as were 351 (91.6%) of 383 proved benign lesions. The demonstration of 58 clinically unsuspected carcinomas indicated that mammography was of value in the detection of carcinoma of the breast before signs and symptoms appeared. Accurate results in mammography have been made possible only by the development of a high milliamperage-low kilovoltage roentgenographic technique. The procedure is safe, simple, easily reproducible, and acceptable to the patient. It can be decisive in the diagnosis of normal, benign, and malignant conditions of the breast. Many clear-cut and specific applications of mammography have evolved during this experience; other applications need further evaluation.