Background: Knowledge about appropriate use of antimicrobials (AM) in the population is an important factor to achieve a proper use of these drugs. Objective: To evaluate the impact of an educational intervention on knowledge about appropriate use of AM in respiratory tract infections in adolescent from Lo Barnechea, Santiago. Methods: Prospective study. We evaluated the level of knowledge about appropriate use of AM in a group of adolescents from two municipal schools in Lo Barnechea. Then, in one of these schools, we made an educational intervention consisting of two workshops. Initial survey was repeated at the end of the first educational session and 4 months after completing the intervention. Results: We applied the knowledge survey to 489 students. The baseline rate of approval was 40.2%. After the first workshop this percentage improved to 74.5% (P = 0.0001), and at 4 months after the educational program finished, the approval rate was 59.1%. Conclusions: There are significant gaps in the level of knowledge about appropriate use of AM in the study population, which significantly improved after an educational intervention. Benefit was maintained for at least 4 months