Protein C and S are important factors in blood coagulation reported in many papers about people who suffered from thromboembolic diseases related to inherited or acquired deficiencies. Homozygous protein C/S deficiency is lethal in most cases without therapy. Heterozygous deficiency is moderate and complications occur between the 20.-50. year of age. Acquired protein C/S deficiency is a strong parameter for liver function. The typical clinical manifestations of protein C/S deficiencies are superficial and deep leg vein thrombosis, thrombosis of the mesenterial, cerebral, renal and axillary veins, portal vein thrombosis and pulmonary embolism. Most of the affected people live disease free over a longer period and develop thromboembolic complications during and after trauma, surgical interventions, pregnancy and puerperium. We report our experience with a 60 years old male who had developed a severe bilateral iliofemoral vein thrombosis with signs of pulmonary embolism after total hip replacement. An extended functional protein C deficiency (type II) was investigated by coagulation tests (Protein C Reagent, coagulometric from Behring Institute). A second female patient developed a descending iliofemoral vein thrombosis during pregnancy. Venous thrombectomy with arteriovenous fistula was performed, but reocclusion occurred after delivery. Redo-surgery was undertaken and a second reocclusion took place 10 days later. Further lysis therapy was not able to reopen the venous system. Whereas immunological and functional protein C levels showed normal ranges, the functional protein S level was markedly reduced (IL-Instrumentation Laboratory Protein S-Test).