Congenital factor XIII (FXIII) deficiency is an extremely rare, yet potentially life-threatening, bleeding disorder, with a 30% rate of spontaneous intracranial haemorrhage. Routine prophylactic management is recommended for all individuals with clinically relevant (FXIII) deficiency and for all symptomatic individuals with congenital factor deficiency. Fibrogammin P is a purified, pasteurized concentrate of FXIII that appears to carry negligible risk of viral transmission, unlike other unprocessed products containing FXIII. An ongoing Phase II/III study of Fibrogammin P in patients with congenital FXIII deficiency is being conducted to evaluate the prophylactic efficacy and long-term safety of this product. Using retrospective chart review data from subjects enrolled in the Phase II/III study, the current analysis was designed to compare spontaneous bleed-event rates prior to and after the initiation of Fibrogammin P prophylaxis. Seven subjects were evaluable for comparison, having received no other prophylactic FXIII-containing product during the 24 months prior to study entry. The mean annual number of spontaneous bleeds was 2.5 events per year prior to Fibrogammin P prophylaxis and 0.2 events per year during Fibrogammin P prophylaxis (P = 0.01). Patients reported no severe bleeds during Fibrogammin P therapy. This small sample supports a consistent and clinically meaningful reduction in spontaneous bleeding with prophylactic use of Fibrogammin P.