Two patients who presented with active bleeding and were diagnosed with acquired hemophilia A (AHA) are reported herein. One was a 27-year-old woman who experienced spontaneous oozing from an episiotomy wound six days after her second normal delivery. Bleeding became progressively worse, despite treatment with primary sutures and curettage of the uterus at a local hospital. She underwent emergency exploratory laparotomy because of intra-abdominal bleeding, during which perforations of the uterus were discovered. Unremitting bleeding from the surgical wound occurred after surgery. The patient was finally diagnosed with AHA when Factor VIII (FVIII) inhibitor (titer, 19 Bethesda units (BU)/ml) was detected in her plasma. She died of refractory hemorrhaging, despite intensive treatment with Factor IX concentrate infusion and cyclophosphamide therapy. The second patient was a 22-year-old man who sustained spontaneous and recurrent intramuscular hemorrhage in the right thigh for one month. Laboratory studies including complete blood count, biochemical evaluation, coagulation screening and immunologic assays were all within normal limits, except for a prolonged activated partial thromboplastin time. Idiopathic AHA was diagnosed after the detection of plasma FVIII inhibitor with a concentration of 5.9 BU/ml. The patient's coagulopathy was successfully managed with plasma exchange and subsequent treatment with oral prednisolone and cyclophosphamide.