A new case of congenital hypodysfibrinogenemia associated with a thrombotic tendency (thrombosis of the peroneal artery, the pulmonary artery and the deep veins of the lower extremities), is reported. Clotting time using Reptilase was significantly prolonged. The low levels of plasma fibrinogen were demonstrated using both thrombin time (Clauss) method (45.0 mg/ml) and radial immunodiffusion technique (106.1 mg/ml). The fibrinogen is also characterized by a defective polymerization of fibrin monomers. Furthermore, the important functional property of this fibrinogen is that the patient's fibrin adsorbs approximately 31-38% of added tissue-plasminogen activator (t-PA) at the time of fibrin formation, whereas control fibrin can adsorb about 79% of added t-PA. This result could provide an explanation for the thrombotic tendency in this patient. This variant fibrinogen appears to have unique characteristics and has been designated as "Fibrinogen Date," according to the city where the proband has lived.