Research shows that asking questions can fundamentally change behavior. We review literature on this question-behavior effect, which demonstrates that asking questions changes both normal and risky behaviors. We discuss potential explanations for the effect and review recent findings that reveal interesting moderators of the influence of questions on behavior. We then highlight the potential impact of the question-behavior effect in an important public health context: screening adolescents for risky behavior. While medical guidelines emphasize the importance of asking adolescents questions about substance (drug, alcohol) use and sexual behaviors, research on the question-behavior effect suggests that asking adolescents about risky behaviors has the potential to increase the frequency with which they engage in these behaviors. We argue that the act of screening or measuring risky behavior is potentially counterproductive. We emphasize the importance of interventions beyond screening, and suggest ways in which screening can be carried out to minimize its impact. In short, asking questions about behaviors can change behavior, and asking questions about risky behaviors may itself be a risky undertaking.The issue of when or how to talk to children about behaviors that parents view negatively is one that all parents must address as their children approach and progress through adolescence. While we might like to pretend that our children would never engage in risky behaviors the reality of teenage life is quite sobering. In the United States each year, there are 831,000 pregnancies among women aged 15-19 years, an estimated 9.1 million cases of sexually transmitted diseases among persons aged 15-24 years, and an estimated 4,842 cases of HIV/AIDS among persons aged 15-24 years. The prevalence of these conditions is partially caused by sexual behavior among adolescents: 46.8% of high school students have had sexual intercourse at least once, and 37.2% of sexually active high schoolers did not use a condom during their last sexual episode. In the past 30 days, 43.3% of our children have drunk alcohol, 9.9% have driven a car or other vehicle when they had been drinking alcohol; 18.5% have carried a weapon; and 20.2% have used marijuana. In the past 12 months, 28.5% of students nationwide have felt so sad or hopeless almost every day for more than 2 weeks in a row that they stopped doing some usual activities, and 13% of students have made a suicide plan. 8.4% of teens have actually attempted suicide in the past year (Centers for Disease Control, 2007). How can we know if our own children are at risk? Should we, as parents and public policy makers, ask children about these issues? If so, what should we say?Our focus in this paper will be on interacting with children about what we refer to as "risky behaviors" or "vices." Examples of these behaviors are listed above, and are referred to as