This study tested a structural equation model linking reinforcement sensitivity to subsequent emotionbased impulsivity (i.e., positive and negative urgency), alcohol use, and risky sexual behavior among a sample of 753 undergraduate drinkers. A hypothesized Sensitivity to Punishment (SP) x Sensitivity to Reward (SR) interaction significantly predicted both positive and negative urgency. At low levels of SR, SP had a significant negative effect on positive urgency and a significant positive effect on negative urgency. However, at high levels of SR, SP had significant positive effects on both types of urgency. Results indicated that positive and negative urgency mediate the associations between reinforcement sensitivity and both alcohol use and risky sexual behavior. Moreover, results demonstrated that at low levels of SR, SP is indirectly associated with decreased alcohol use. However, as SR increases, SP is indirectly associated with increased alcohol use and risky sexual behavior, due to the joint effect of high SP and SR on emotion-based impulsivity.