Recently, Feldman, Joorman, and Johnson (in press) proposed that differences in the ways individuals respond to positive affect (PA) might impact the length and intensity of PA episodes, perhaps leading to changes in long-term mental and physical health. Feldman et al. (in press) suggested that "positive rumination," repetitive positive self- and symptom-focused responses to positive mood, should enhance PA, whereas "dampening" responses should diminish PA. The Response to Positive Affect Scale (RPA; Feldman et al., in press) was created to measure these constructs. Preliminary research has found that measures of positive rumination and dampening help predict mania and depression symptoms. The current study examined the convergent and predictive criterion validity, and reliability of the constructs of positive rumination and dampening through a combination cross-sectional, experimental, and naturalistic follow-up design. Temple University undergraduates (Phase I N = 1,281, Phase II N = 181, Phase III N = 154) participated in a three-phase study. In Phase I, participants completed the RPA along with a series of positive and negative health and cognition measures. In Phase II, participants were randomly assigned to one of three mood induction groups (negative, neutral, or positive) and completed a series of affect reports over time. One month later, Phase II participants were asked to report on their affect, physical health, mental health, and intervening life events during Phase III. As expected, positive rumination and dampening demonstrated convergent and divergent validity. However, the predictive criterion validity results were mixed, with the constructs predicting some, but not all, responses to mood inductions. The naturalistic follow-up demonstrated that positive rumination interacted with positive life events to predict hypothesized changes in psychological health, but not physical health. The test-retest reliability of the RPA was not acceptable for a trait measure. These results suggest that positive rumination and dampening are important constructs involved in both mental health and illness. Future research should consider alternative strategies for measuring responses to PA, including more realistic experimental paradigms. / Psychology