While venous manifestations are common in Behçet disease and often occur as a presenting feature, thromboses of the vena cava are less frequent and usually occur several years after onset. We report the unusual case of a patient whose Behçet disease was revealed by vena cava thrombosis. Most authors underscore the difficulties encountered in ascribing vena cava thrombosis to Behçet disease and the frequent latency of inferior vena cava involvement. Pathological changes in these venous thromboses are identical to those found in other organs involved in Behçet disease: they consist in inflammation of the venous wall with perivascularitis and secondary thrombosis. Lastly, there is a general agreement as to the adverse prognostic significance of the venous involvement.