PREVENTION OF RECURRENT VENOUS THROMBOEMBOLISM (PREVENT) TRIAL The best way to manage patients who have experienced a first idiopathic deep venous thrombosis is a controversial topic. Current regimens of full-dose warfarin are clearly effective for short-term prophylaxis, so the question is: How long should patients be kept on antithrombotic therapy? Guidelines from the American College of Chest Physicians suggest 3 months of oral antithrombotic therapy with warfarin; other clinicians advocate oral anticoagulant therapy for six months. Yet data presented by Prandoni et al. (Annals of Internal Medicine 1996; 125:1-7) demonstrate that 25% of patients will suffer a recurrence within five years; an even greater percentage will suffer a recurrence when the index event is not surgery or trauma The Prevention of Recurrent Venous Thromboembolism (PREVENT) Trial is evaluating the effectiveness of prolonged treatment with low-dose warfarin in preventing a recurrent venous thromboembolism. This randomized, double-blind, placebo-controlled trial is comparing the combination of usual care and targeted low-dose warfarin with usual care plus placebo. Eligible patients include men and women age 40 and older who are free of metastatic cancer, who have experienced an idiopathic venous thromboembolism and who have completed a standard course of outpatient anticoagulation within the past two years. They will be followed for up to four years. The study, funded by the National Heart, Lung, and Blood Institute, is being conducted at 45 sites around the U.S., including the University of Massachusetts. It is headquartered at the Division of Preventive Medicine, Brigham and Women's Hospital, Boston. The principal investigator is Paul M. Ridker, MD.