An 81-year old woman suddenly developed extensive ecchymosis. A factor VIII:c inhibitor was detected. She received porcine factor VIII, corticosteroids, intravenous immunoglobulins and cyclophosphamide. Normalization of factor VIII level was achieved in 1 month. The patient died, 3 months later, of congestive heart failure. Spontaneous development of factor VIII inhibitors is an extremely rare event which usually occurs in dramatic bleeding. Many associated diseases have been reported. Patients with serious bleeding should be given porcine factor VIII. Immunosuppressive therapy consists of corticosteroids, cyclophosphamide and intravenous immunoglobulins.