Mixed findings on state positive affect, typically assessed just before an exposure/extinction session, as a predictor contradict more consistent evidence from clinical trial data that baseline levels of trait positive affectivity (i.e., positive emotionality) can predict exposure therapy outcome. As such, questions remain about the best way to assess positive affectivity as a potential treatment moderator. This study was designed to investigate: (1) the predictive influence of state and trait-positive affect on the outcome of a single-session virtual reality exposure intervention for public speaking anxiety in college-aged adults, and (2) the correlates of trait-positive affectivity that are most associated with the expected outcome prediction for that variable. State affect is manipulated at an experimental level with affect induction procedures; trait positive affectivity is measured at baseline. Three dependent measures - a primary outcome of public speaking anxiety and secondary outcomes of social phobia and self-reported valence to giving a speech - are measured immediately post-intervention and at a one-week follow-up.