Patients with disorders of hemostasis are subject to long term problems and risks, difficult treatment decisions and risks associated with treatment itself. Many of these risks and complications can be lessened or prevented by appropriate intervention strategies. Advances in the management of patients with bleeding disorders of relatively low incidence require: 1) that clinical studies utilize a multi-institutional cooperative network in order to accrue sufficient numbers of patients to achieve meaningful answers; and 2) that patients be educated on the vital importance of participation in such studies. The purpose of this project is to develop a Hemostasis Core Clinical Research Unit at Tulane University as part of the NIH Transfusion Medicine/Hemostasis Clinical Research Network. This Unit will be developed using some of the basic infrastructure and services of the Tulane Center for Bleeding Disorders, which is dedicated to the care and advancement of patients with disorders of hemostasis. Once established, this Core Research Unit will provide access to clinical trials for hemostasis patients from the Center for Bleeding Disorders, the Bone Marrow Transplant Unit and from throughout the network of Tulane affiliated hospitals and clinics. In addition, two clinical trial protocols have been developed as part of this proposal. The first, A prospective randomized crossover study of activated prothrombin complex concentrates (aPCCs) as prophylactic therapy in hemophilia A patients with inhibitors, is a long-term protocol designed to evaluate the efficacy of aPCCs in the prevention of bleeds in this very complicated group of patients. The second, short-term protocol, A prospective study of ribavirin for the treatment of HIVassociated immunopathic thrombocytopenic purpura (ITP), was developed to test a novel pharmacologic agent in the management of HIV-ITP.