Background: In Mexico, the state of Veracruz occupied the second national place in the number of HIV / AIDS cases during 2019. The total cases registered in Veracruz, 5.8% were in young people between 15 and 19 years old. Objective: To determinate the association between the level of knowledge about HIV / AIDS and risk behaviors in high school students. Methods: A cross-sectional, prospective, analytical and observational study was carried out. High school students from the city of Veracruz-Boca del Río, Mexico with active sex life were included, students who refused to participate were excluded. The WHO Behavior Assessment Test and the HIV / AIDS-65 were apllied. The surveys were conducted through Google Forms® and were answered on that same platform in an electronic device with internet. For the data analysis the SPSS v22 software. Results: 895 students were interviewed, of which 363(40.55%) had active sex life and 3(0.8%) reported being HIV positive. Sexual orientation, having sexual activity under the consumption of illicit substances, being monogamous or promiscuous, initiate sexual life early, the frequency in the use of condoms, accepting to take Prep or Pep in case of having risk relationships had no association with the high level of knowledge about HIV (p>0.05). Use condoms in the first sexual relationship (OR 1.8, 95%CI 1.94-3.2), susceptibility (OR 3.1 95% CI 1.6-6.8), negative attitude (OR 0.04, 95%CI 0.01-0.1), autonomy (OR 2.5, 95%CI 1.5-4.0) and positive attitude (OR 2.3, 95% CI 1.4-3.9) with p value <0.05. Conclusions: the high level of knowledge in students with active sexual life is only associated with the use of condoms during the first sexual intercourse, without presenting differences to modify other risk behaviors or the intention of taking Prep or Pep in case of anticipating the need of using it.