Two patients with classical hemophilia, and twins with a combination of classical hemophilia and von Willebrand’s disease, were treated prophylactically with cryopercipitate for periods up to two years. All had significantly fewer spontaneous hemorrhages during therapy. The prophylactic regimen required to prevent spontaneous hemorrhage was different in each case. Progressive enlargement of an inoperable hemophilic pseudotumor was arrested in one. Complications encountered included hepatitis in one case and occasional urticaria in another. Prophylactic treatment appears to be practical and indicated in selected cases.