Experience with a dedicated breast CT scanner (General Electric CT/M) using a contrast medium enhancement technique indicates that CT is superior to mammography, thermography, or physical examination for diagnosing both benign and malignant mammary disease especially in dense, thick, or fibrocystic breasts. CT is capable of diagnosing totally unsuspected early miniature carcinomas. It can identify and differentiate potential precancerous lesions from benign fibrocystic disease, and is the diagnostic tool of choice for evaluating and following severe fibrocystic disease. CT evaluation also affords definitive diagnostic help in instances where the mammographic, thermographic, and/or physical examinations are inconclusive. It can influence immediate surgical intervention or mitigate against an unnecessary biopsy. The study not only demonstrates morphologic changes in the breast but also accurately depicts an altered iodine pool in mammary tissues.