The lupus anticoagulant is a well-described in vitro phenomenon that may be associated with arterial and venous thrombotic episodes. The lupus anticoagulant is never accompanied by a hemorrhagic diathesis unless it is associated with a second coagulation abnormality such as thrombocytopenia or hypoprothrombinemia. The lupus anticoagulant-hypoprothrombinemia syndrome is now a well-defined entity that may cause a severe, life-threatening hemorrhagic diathesis. The hypoprothrombinemia in this syndrome is the result of rapid clearance of prothrombin-antiprothrombin antibody complexes by the reticulo-endothelial system. The cause of antiprothrombin antibody formation is unknown. The authors describe a recent experience with a patient with this syndrome who initially had recurrent, life-threatening gastrointestinal bleeding. They were able to demonstrate hypoprothrombinemia and the presence of prothrombin-antiprothrombin antibody immune complexes. The patient was treated with prednisone, with correction of the bleeding disorder; however, the patient had resultant death from thrombosis. A literature review of the past 30 years as it relates to the discovery and treatment of this phenomenon is included.