Sexuslly transmitted diseases are a major public health problem in the whole world, and significantly affect the quality of life, causing serious morbidity and mortality. They occur in a sexually active population, and with the exception of the reproductive system, they can also affect other body systems. If they are not treated, serious complications can occur. A great emphasis is placed on the preventive. Important risk factors for the development of sexually transmitted infections include early sexual intercourse, promiscuous behavior and not using condoms. In Croatia, 20% of fifteen-years-olds have already engaged in sexual relations. Education should be carried out in primary and high schools, but not as a part of classroom lesson, but as a separate subject led by professionals (doctor, nurse). During education, basic information should be provided in an understandable language, encourage the development of self-esteem and responsible sexual behavior. The aim of this research was to assess the level of knowledge of young people about chlamydia, gonorrhea and syphilis. The anonymous survey questionnaire was available on Facebook and Instagram from January 26, 2023. to July 6, 2023. 103 respondents from the first to the fifth grade of high school participated. Students shown good knowledge about the most common bacterial sexually transmitted infections. The last three questions in the questionnaire were related to the use of protection during sexual intercourse, self-assessment of education and the role of the nurse in the education of sexually active people. 19% of respondents don't use protection, and 35% of respondents believe that they are sufficiently educated about sexually transmitted infections. 86% of respondents believe that nurses have a major role in the education of young, sexually active people.