Impulsivity has been a widely explored construct, particularly as a personality-based risk factor for addictive behaviors. The authors review evidence that (a) there is no single impulsivity trait; rather, there are at least five different personality traits that dispose individuals to rash or impulsive action; (b) the five traits predict different behaviors longitudinally; for example, the emotion-based urgency traits predict problematic involvement in several risky behaviors and sensation seeking instead predicts the frequency of engaging in such behaviors; (c) the traits can be measured in preadolescent children; (d) individual differences in the traits among preadolescent children predict the subsequent onset of, and increases in, risky behaviors including alcohol use; (e) the traits may operate by biasing the learning process, such that high-risk traits make high-risk learning more likely, thus leading to maladaptive behavior; (f) the emotion-based urgency traits may contribute to compulsive engagement in addictive behaviors; and (g) there is evidence that different interventions are appropriate for the different trait structures.