This review concentrates on those disorders in which superficial thrombophlebitis can be a significant or presenting clinical sign. Primary hypercoagulable states are those conditions associated with an increased risk of thrombosis caused by a specific measurable defect in the proteins of coagulation and/or fibrinolytic systems. These disorders are frequently inherited and include deficiencies of antithrombin III, heparin cofactor 2, protein C, protein S, abnormal fibrinolytic activity, dysfibrinogenemia, and Hageman trait. Patients with a lupus anticoagulant and anticardiolipin antibody syndrome with thrombotic episodes are also considered to have a primary hypercoagulable state. The physiology, pathophysiology, clinical characteristics, and treatment of primary hypercoagulable states are reviewed.