Congenital deficiency of antithrombin III is considered as one serious primary hypercoagulable state. The authors present a case of deficiency of antithrombin III in a 28 years old young male, with aortic valve disease and several thromboembolic events. When discussing their diagnostical and therapeutical aspects they call the attention to the need for investigation of the situations in which thrombophilia presents with recurrent venous and arterial thrombosis.