Trait anxiety is a relatively stable disposition reflecting an individual's tendency to experience anxious symptomatology, typically measured using questionnaires such as the Spielberger Trait Anxiety Inventory (STAI-T). While trait anxiety commonly is considered a unitary construct, recent questionnaire research suggests that two different dimensions of anxiety vulnerability account for independent variance in trait anxiety scores. These dimensions are anxiety reactivity (AR), reflecting the intensity of anxiety reactions to stressors, and anxiety perseveration (AP), reflecting the persistence of anxiety symptoms. This study investigated whether in vivo measures of these two facets independently contribute to anxiety vulnerability. Seventy-two participants were exposed to a novel stress task designed to yield measures of AR and AP. Regression analysis determined that these in vivo measures were unrelated to each other, and each accounted for independent variance in trait anxiety scores. The implications of these findings for the assessment and understanding of anxiety vulnerability are discussed. © 2013 Taylor & Francis.