Primary hypercoagulable states are hereditary disorders that result in arterial and venous thromboses. The purpose of this report is to present three patients with hypercoagulable states, and offer current guidelines for diagnosis and treatment. Primary hypercoagulable disorders such as antithrombin III, protein C and protein S deficiencies, fibrinolytic disorders such as decreased plasminogen levels and plasminogen activator deficiency, and antiphospholipid syndromes such as anticariolipin antibody and lupus anticoagulants will be reviewed. We will emphasize clinical characteristics that should prompt evaluation for hypercoagulation, appropriate laboratory tests for hypercoagulable disorders, and treatment. Other secondary and recently investigated hypercoagulable disorders, including heparin-associated thrombocytopenia, homocystinemia, lipoprotein (a), plasminogen activator inhibitor, and factor V Leiden, will also be reviewed.