We describe a new congenital dysfibrinogenemia: fibrinogen Barcelona II in 8 members of a family with no major bleeding or thrombotic tendency. Incubation of this fibrinogen with thrombin at low concentration releases half of the expected normal fibrinopeptide A (FPA) and with some delay it releases an abnormal FPA. Abnormal FPA was purified and sequenced and showed a change in the normal amino acid sequence: arginine in position 16 has been substituted by a histidine. This is another case of dysfibrinogenemia in which Aα 16 Arg → His has been identified as the cause of abnormal behavior of the fibrinogen molecu