Edgar J Poth lecture. Pathogenesis, diagnosis, and treatment of thrombosis. Thrombosis and its major sequela, embolism, continue to contribute significantly to morbidity and mortality, both as primary disorders and as complications of other systemic systems. The understanding of the etiology of thromboembolism and the role of platelets, endothelium, and the plasma proteins in the development of thrombotic disorders has recently improved. Other blood cells, in particular neutrophils, have been suggested as possible mediators of thrombosis in clinical disorders characterized by decreased capillary blood flow. Newer imaging techniques such as duplex scanning have improved the accuracy and ease of diagnosis. Thrombolytic therapy is a more physiologic approach to the management of thrombosis, but its role is limited by systemic fibrinolysis. The development of fibrin-specific agents and better delivery techniques in combination with thromboembolectomy and anticoagulation should improve the management of patients with thrombosis. 