Positive emotion has been shown to be associated with adaptive outcomes in a number of domains, including psychological health. However, research has largely focused on overall levels of positive emotion with less attention paid to how variable versus stable it is across time. We thus examined the psychological health correlates of positive emotion variability versus stability across 2 distinct studies, populations, and scientifically validated approaches for quantifying variability in emotion across time. Study 1 used a daily experience approach in a U.S. community sample (N = 244) to examine positive emotion variability across 2 weeks (macrolevel). Study 2 adopted a daily reconstruction method in a French adult sample (N = 2,391) to examine variability within 1 day (microlevel). Greater macro- and microlevel variability in positive emotion was associated with worse psychological health, including lower well-being and life satisfaction and greater depression and anxiety (Study 1), and lower daily satisfaction, life satisfaction, and happiness (Study 2). Taken together, these findings support the notion that positive emotion variability plays an important and incremental role in psychological health above and beyond overall levels of happiness, and that too much variability might be maladaptive. (PsycINFO Database Record (c) 2013 APA, all rights reserved).