This study was carried out to collect basic information on the knowledge and attidutes and behavior related to the prevention of breast cancer of a Sample Seoul women. Similar studies had dealt with samples of tumor clinic patients and thier families and with non-professional hospital workers. The sample for this study was drawn by women out patients from eight centrally located general hospitals, in Seoul where the number of annual out patients exceeded 100,000, and the number of beds exceeded 100. The interview schedule conisted 33 questions related to knowledge, attitude, and behavior related to prevention of breast cancer. It was modified from the previous on cancer studies. The investigator interviewed 665 women over 20 years of age, from those who visited these eight hospitals from 24, June to 20, August 1975. More than half of the respondents were housewives and primarily in the 20 to 29 ages group. They had a mean level of 3.562 pregnancies and 1,986 children. 33.4% were high-school graduates, 32.2% had a monthly family income in the 50,000 to 100,000 won range. 75% of the respondents had heard about breast cancer through mass media or personal media, but the majority of respondents did not have an accurate understanding of it. This varied according to educational, economical income and occupations. The primary reason given for maintaining distance from a patient with breast cancer was not because of cancer but simply because person was a patient. 74. 7% of the respondents thought that early cancer of the breast could be cured with early treatment. Only 5.3% of the respondents had ever had a physical examination and only 6. 3% practised self examination of the breast.