As a cause of death in women, breast cancer ranks second to stomach cancer in Korea. Age-standardized mortality rates for breast cancer steadily increased during the 1980s and 1990s. There are big differences in the incidence rates for breast cancer compared with Western countries. Epidemiological features, trends in morbidity and mortality, various age-specific incidence curves, migrant study results, and analysis of the risk factors, however, suggest that the incidence of breast cancer might be further increasing in Korea. The key epidemiological hormonal risk factors for breast cancer are all explicable in terms of the estrogen augmented by progesterone hypothesis. These include older age, family history of breast cancer, early menarche, late menopause, late full-term pregnancy, and never a breast feeding. Both the establishment of high-risk groups and the estimation of lifetime risk are essential to develop a control strategy against breast cancer. Invasive ductal carcinoma is the most common histologic type of breast cancer in Korea, and the five-year survival rate has been estimated as 80-83%. Recent studies on the identification of susceptibility factors such as genetic polymorphisms of GSTM1/T1/P1, COMT, CYP2E1, CYP19, CYP17, ER-alpha, XRCC1, XRCC3, RAD52, TGF-alpha, TNF-alpha, IL-1B, IL-1RN, CDK7 etc. that predispose individuals to breast cancer by gene-environment or gene-gene interactions may possibly give further insight into both the etiology and the prevention of this malignancy.