Purpose: The purpose of this study was to identify knowledge, attitude, and practice of middle-aged women breast self-examination, and to develop a breast self-examination promotion program for them. Method: The subjects of the study were 365 middle-aged women in Seoul, Busan, Daegu, Daejeon, Gyeongbok, Gyeongnam, Jeonbuk, Gangwon, and Kyonggi. The instruments used in this study included knowledge (l6items), attitude (22items) by Choi (1996) and practice (1item). The data were collected from September 15 to October 31, 2001 by using self-administered questionnaire. The data were analyzed by using descriptive statistics, Pearson correlation coefficient, $x^2$ test, t-test, ANOVA and Scheffe test with SPSS program. Results: 1) 78.4% of the subjects were educated for breast self-examination. The most common source of knowledge for the breast self-examination was mess media. 2) The average score of knowledge on breast self-examination was 8.52 points. The average score of attitude toward breast self-examination was 3.08 points. 58.3% of the subjects practiced breast self-examination. But only 9.4% of the subjects practiced breast self-examination with a monthly basis. 3) Knowledge on breast self-examination was correlated with demographic variables including residence (F=2.923, p=0.004), education (F=5.145 p=0.000), number of children (F=5.125 p=0.002), family income (F=6.128 p=0.002), and menopause (t=-2.330, p= 0.020). Attitude toward breast self-examination was correlated with demographic variables including residence (F=3.611, p=0.000), age (F=2.731 p= 0.029), education (F=4.480 p=0.004), and family income (F=5.963 p=0.003). Practice of breast self-examination was correlated with demographic variables including residence ($x^2$=51.342, p=0.000), education ($x^2$=19.896, p=0.000), and menopause ($x^2$=9.841, p=0.000). 4) In terms of correlations among the scores of breast self-examination related knowledge, attitude, and practice, there was a correlation between knowledge and attitude. But there was no correlations between knowledge and practice, and between attitude and practice of breast self-examination. Conclusion: This study suggests that programs about the practice of breast self examination need to be developed in the future.