Not only the incidence but also the mortality of female breast cancer has been steadily increasing in Korea since the 1980s. Epidemiologic evidence on changes in lifestyle and risk factors related with breast cancer, and data from migrant studies strongly suggest that breast cancer might further increase. In order to estimate the long-term trend in mortality of breast cancer in Korean women, we analyzed age-specific mortality rates for breast cancer over the past 20 years, and made a projection up to 2020 using a linear regression model with the Poisson distribution. The age-adjusted mortality rates for breast cancer per 100,000 persons were 2.84 in 1983, 4.91 in 1993, and 6.26 in 2003. The predicted expected age-adjusted mortality rates for breast cancer are 6.51 for 2005, 7.37 for 2010, 8.22 for 2015, and 9.07 for 2020, with an estimated annual increment of breast cancer mortality of 0.1704. Accordingly, 1,564 women in 2005 and 3,087 in 2020 will be expected to die of breast cancer in Korea. Compared with the rate in 1983, this indicates a more than 3-fold increase by 2020. On the basis of our results, female breast cancer in Korea will linearly increase for the forseeable future if the trend over the past 20 years continues.