Abstract: This study assessed the consistency of self-reports of risk behavior (overall and within four specific domains: alcohol use, tobacco use, drug use, and sexual activity) in two editions of the Brazilian National School Based Survey of Adolescent Health (PeNSE): 2009 and 2012. The overall proportion of cases with at least one inconsistent response in the two editions was 11.7% (2.7% on the alcohol items, 2.1% for drug use, 4.3% for cigarette use, 3% for sexual activity) and 22.7% (12.8% on alcohol items, 2.5% for drug use, 4.3% for cigarette use, 4.1% for sexual activity), respectively. Such inconsistency was more prevalent among males, delayed students, those who reported having experimented with drugs, and those who did not have a cellphone. Because inconsistent responses were more prevalent among the students who claimed to have engaged in risky activities, removing inconsistent responders affected the estimated prevalence of all risk behaviors in both editions of the survey. This study supports the importance of performing consistency checks of self-report surveys, following the growing body of literature on this topic.