RESUMEN
Objective:To identify the knowledge of Sexual Transmitted Diseases (STD) in adolescents before and after an educational intervention.Study Design:Quasi-experimental, longitudinal study Place and Duration of Study:This study was conducted in the Family Medicine Unite Number 6 of the Mexican Institute of Social Security, Puebla, Mexico during January to April in 2017.Methodology:151 patients were included in whom theknowledge level in sexual transmitted diseases were correlated. A study was used to measure the knowledge in the anatomy and sexual physiology, STDs prevention and ant conceptive. Central tendency and dispersion measures were employed for numeric variables and frequency (proportions) measures for categorical measures. Results:A total of 151 adolescents with (58.9%) are female 17 years of age, 97.4% without partner and 74% without sex life. The knowledge after an educational intervention increased 10.6% in comparison to before the intervention. The statistical treatment was based on the Wilcoxon, resulting in a p=0.000. Conclusion:The knowledge of STDs in adolescents increased after an educational intervention