We have recently experienced a case of mammary hamartoma in 29-year-old woman. Hamartoma of the breast is a rare benign tumor-like lesion which is characteristically well demarcated by thin layer of fibrofatty tissue and composed of essentially normal mammary tissue with mammary glandular structure and fibrous stroma containing variable amounts of fat. The lobular architecture is relatively well preserved. It can be readily recognized, but should not be confused with fibroadenoma or mammary dysplasia. It also shows characteristic mammographic picture.