ABSTRACTRumination and worry are two perseverative, negatively valenced thought processes that characterise depressive and anxiety disorders. Despite significant research interest, little is known about the everyday precipitants and consequences of rumination and worry. Using an experience sampling methodology, we examined and compared rumination and worry with respect to their relations to daily events and affective experience. Participants diagnosed with Major Depressive Disorder, Generalized Anxiety Disorder, co-occurring MDD–GAD, or no diagnosis carried an electronic device for one week and reported on rumination, (...) worry, significant events, positive affect, and negative affect. Across the clinical groups, occurrences of everyday events predicted subsequent increases in rumination, but not worry. Further, higher momentary levels of rumination, but not worry, predicted subsequent decreases in PA and increases in NA. Thus, in these clinical groups, rumination was more susceptible to... (shrink)