Introduction: Sexual health education provides young people with accurate, age-appropriate information about sexuality and their sexual and reproductive health, which is very important for their overall health. The aim of this study is to determine the knowledge and attitude school-based towards sexual health education among high school students in Bulgaria. Material and methods: A cross-sectional study design was used to determine the knowledge and attitude towards reproductive and sexual health education among high school students. A total of 315 adolescents in the age group of 15-19 years were surveyed using a self-report questionnaire. Girls being predominant - 56.2% (n=177). Data was analyzed using descriptive statistic and nonparametric tests. Results: A significant part of the respondents did not attend a health lecture in the current year (40.0%; n= 126), and most often received health information from books, brochures, magazines (31.4%; n=99), followed by friends and relatives (24.8%; n= 78). Most of the respondents have good knowledge about preventing unwanted pregnancy (82.9%; n= 261) and sexually transmitted diseases (85.7%; n= 270), with girls being better informed about both the questions (P=0.019; P=0.000). 36.2% (n=114) of the respondents have ever had sex. The mean age at first sexual initiation was 15.56±1.761 years. Conclusion: High school students have a good knowledge of sexuality and sexual and reproductive health, but they receive this information mostly outside of school. There is a need for teachers to be engaged in effective teaching of sexual health education to high school students in order to improve the quality of their knowledge and attitudes towards sex. [For the complete proceedings, see ED672804.]