Aplastic anemia is a bone marrow disease characterized by marrow aplasia and pancytopenia. Because hematopoietic stem cell transplantation (HSCT) cures severe aplastic anemia (SAA), it is the treatment of choice for younger patients. For many years, antithymocyte globulin (ATG) has been standard immunosuppressive therapy for those aplastic anemia patients that have no HLA matched related donor. ATG significantly improves aplastic anemia outcome, especially when combined with cyclosporine (CSP). The response rate varies from 40% to 70% and long-term survival is comparable with patients receiving marrow transplant. From 1983 until 2006, 46 SAA patients received HLA identical sibling marrow graft. In the same period, 50 patients received standard immunosuppressive therapy combined from horse or rabbit ATG, 6 methyl prednisolone and cyclosporine. Out of 46 transplant patients, 27 received a combination of cyclophosphamide and thoraco-abdominal irradiation. The overall probability of survival for SAA patients that underwent marrow grafting is 51%, and for patients receiving immunosuppressive treatment 20%. We analyzed a cohort of patients receiving treatment after 1990 and found the probability of survival to be 64% for bone marrow transplanted patients and 36% for patients receiving immunosuppression. Infection is the main cause of death in both groups. In conclusion, we documented improving results using ATG in patients with SAA.