Both animal and human data implicate psychosocial distress and cardiovascular reactivity in response to challenge in the etiology of sudden cardiac death. In this study, the relation of these biobehaviorial factors to frequency of ventricular premature complexes, a predictor of sudden death was investigated. The study population was made up of patients enrolled in the National Heart, Lung, and Blood Institute's Cardiac Arrhythmia Pilot Study (CAPS). Ventricular premature complexes (VPCs) were assessed by multiple, 24-hour ambulatory electrocardiographic recordings. Patients completed trait psychosocial measures assessed at baseline and state psychosocial measures assessed periodically during a 1-year follow-up period. Psychosocial measures included self-reports of depression, anxiety, anger and type A behavior pattern. A competitive challenge using a video game was used as a stressor to elicit cardiovascular reactivity and was administered at baseline and during follow-up sessions. Cardiovascular reactivity was defined as peak level during stressor exposure minus the mean of resting levels for systolic and diastolic blood pressure and pulse rate. Results indicated that biobehavioral factors were not associated with diurnal VPC rates. Furthermore, biobehavioral factors did not predict response to antiarrhythmic therapy. Based upon the results of this study, it is speculated that the established relation between behavioral factors and sudden death may not be mediated by VPC rates.