Various aspects of personality or dispositional style predict risk for psychiatric disorders among adults. In particular, signs of neuroticism, emotional reactivity, or sensitivity to stress are strong predictors of later mood or anxiety disorders. The current report extends this literature to adolescents. An epidemiologic sample of 776 young people living in upstate New York received psychiatric assessments based on the Diagnostic and Statistical Manual of Mental Disorders, Third Edition-Revised, (DSM-III-R) and a self-report assessment of personality style in 1983 and 1985. Psychopathology was again assessed in 1992. The current study first examined demographic correlates of emotional reactivity. The study then considered the predictive relationship between emotionally reactive personality style at one study wave and psychopathology at later waves. In middle but not early adolescence, girls showed higher levels of emotional reactivity than boys. In turn, high levels of emotional reactivity predicted a range of psychiatric disorders at follow-up. The most consistent associations emerged for major depression and fearful spells, a term the authors use to describe a subclinical form of panic attacks. As in adults, midadolescent girls rate themselves as more emotionally reactive than midadolescent boys. Moreover, adolescents who rate themselves as emotionally reactive face a high risk for mood and anxiety disorders. High levels of emotional reactivity may represent a manifestation of underlying neurobiologic risk for mood and anxiety disorders.