Currently, cancer is one of the causes of death in the world. Known from summary of pathology center of Indonesia, from 10 types of most common cancer in Indonesia, cervical cancer and breast cancer are at the highest rate. Breast cancer allegedly caused by a complex interaction of many factors such as genetic, hormonal, and environmental. According to the latest registration data from "Research Project at Cipto Mangunkusumo Hospital 1975-1978" the youngest patient are between 20-29 years. In developing countries, 80-90% of cancer is usually not curable because patients come for treatment at an advanced stage. Early detection of breast cancer can be done by BSE(Breast Self Examination). The aim of this study was to apprehend the young women’s knowledge about breast cancer risk factors and BSE (Breast Self Examination). This is a descriptive study with 99 samples. The sampling technique was done by proportional sampling methode. Data were collected by utilizing questionnaire and analyzed by univariate analysis. The results obtained were the knowledge of young women about breast cancer risk factors in SMA in Banda Aceh can be categorized in high category (4 respondents or 4.04%), moderate (75 respondents or 75.75%), and low (20 respondents or 20.20%). While knowledge of young women about BSE (Breast Self Examination) in SMA in Banda Aceh can be categorized in the high category (11 respondents or 11.11%), moderate ( 76 respondents or 76.76%), and low category (12 respondents or 12.12%). Kata kunci : pengetahuan, remaja putri, faktor risiko kanker payudara, sadari (Periksa Payudara Sendiri)