Drug abuse has serious, often lethal, biomedical consequences, such as HIV infection and cardiovascular dysfunction. This project studies subject characteristics, high-risk behaviors, and other factors associated with such consequences, with the goal of developing interventions to prevent or ameliorate them. One study currently underway provides a comprehensive, non-invasive assessment of cardiovascular function in cocaine abusers, using 24-hour ambulatory monitoring of EKG, blood pressure, and heart rate; high-resolution EKG; analysis of heart rate variability (vagal tone), and echocardiography. Evaluation of the subclinical effects of acute and chronic cocaine use on cardiovascular function will help elucidate the mechanisms of cocaine's cardiovascular effects, hopefully leading to their prevention or amelioration.