In Japan, the mortality rate from female breast cancer has increased in recent years. In 1998, the number of deaths from female breast cancer was 8,589, accounting for 7.7% of all female cancer deaths. The estimated number of new cases of female breast cancer in 1995 was 29,818, accounting for 15.3% of all sites, and its age-adjusted incidence rate was 39.8 per 100,000, ranking it top among the main sites of female cancer. As breast cancer is predicted to increase in the future, it is important for the primary prevention of breast cancer to avoid weight gain during adulthood, excess intake of fat, especially animal fat, and a high intake of alcohol. Physical activity and diets high in vegetables and fruits should be promoted.