Congenital deficiency of Factor XIII is a rare but potentially life threatening disorder. It is inherited in an autosomal recessive fashion. Infusion of Factor XIII has proved to be useful for prevention and treatment of bleeding episodes, especially of spontaneous intracranial bleedings. In this study, Fibrogammin P will be given to patients with congenital Factor XIII deficiency and congenital/acquired FXIII deficiency to prevent bleeding and to treat established bleeding episodes. For Factor XIII prophylaxis to prevent hemorrhages, the dosage will depend on the weight of the subject. The frequency of Factor XIII administration will be determined by the factor's circulating half-life. During the first month only, a Factor XIII pharmacokinetic study will be determined over a 4-week period. Safety data will include accrual of information on viral safety, liver function, complete blood counts and adverse events. Historical data concerning spontaneous bleeds will be collected whenever possible two years prior to treatment with Fibrogammin P.