Two siblings with congenital afibrinogenemia received prophylactic infusions of cryoprecipitate in order to prevent serious hemorrhage during early childhood. Three bags (units) of this fibrinogen-containing blood product were administered every 7-10 days for 15 months in one case and 24 months in the other. Hemorrhage was nearly completely prevented during the period of prophylaxis. Side effects from cryoprecipitate were not observed. Prophylactic infusion of cryoprecipitate, made practical by the relatively long half-life of fibrinogen, should be considered in other patients with this disorder.