A total of 184 Black and white children and adolescents of both genders are recruited for participation, half being pre-pubescent (9-10 years old) and half being post-pubescent (15-16 years old). The first laboratory session consists of a fasting venous blood draw, collection of anthropomorphic data, a psychophysiological stress protocol involving four tasks selected to elicit different autonomic nervous system responses, and completion of standardized questionnaires to assess hostility and social support. A second session involves an echocardiographic assessment of left ventricular geometry and cardiac performance variables, the Type A Structured Interview, and an interview examining how subjects process information about hostile intentions and actions of others.