Breast cancer is the most frequent malignant tumor worldwide. In recent years there has been observed an increase in its frequency, especially in developing countries, as Mexico, where mortality is arriving to the first cause of death in females. This is, in part, due to a delayed diagnosis, most frequently done in locally advances stages with a low cure rate. This is a review of all risk factors: age, sex, personal and familial history, genetic syndromes, associated breast disease, geographic distribution, body structure and environmental, hormonal, reproductive and dietary factors. It is concluded that breast cancer is a public health problem in developed and developing countries, and the best methods to drop mortality for breast cancer is the wide use of screening mammography in women at risk, in order to find cancers at initial stages and offer the adequate treatment.