Breast cancer is the third most common malignancy among korean women following uterine cervical and gastric cancers. The incidence of breast cancer is now gradually Increasing. This trend may be seen through early detection from routine check-ups by the clinician and self diagnosis by patients themselves. Other major methods of detection are through the use of mammography and ultrasonography. Breast examinations should be done every month though self examination and every two years by a clinician at ages below 34 and over 65 years old. And women of ages between 35 and 64 years should have a physical examination and mammography screening at intervals one or two years. Sometimes breast ultrasonography is more helpful in younger women and women with dense or postpartum post partum lactating breast. These efforts are helpful for early detection of breast cancer and result in a decreased mortality rate from this cancer.