A number of recent laboratory and prospective field studies suggest that the tendency to ruminate about dysphoric moods is associated with more severe and persistent negative emotional experiences (e.g, Morrow & Nolen-Hoeksema, 1990; Nolen-Hoeksema & Morrow, 1991). The current paper reports two studies that rested the hypotheses that (a) ruminative response styles act as a trait vulnerability to dysphoria, particularly to relatively persistent episodes of dysphoria; (b) aspects of rumination that are not likely to be contaminated with the presence and severity of previous symptomatology (introspection/self-isolation, self-blame) demonstrate vulnerability effects; and (c) rumination mediates the effects of gender and neuroticism on vulnerability to dysphoria. Consistent supper: was found for each of these hypotheses. Overall, our data suggest that rumination might reflect an important cognitive manifestation of neuroticism that increases vulnerability to episodes of persistent dysphoria.