For patients with severe aplastic anemia (SAA) who have failed to respond to immunosuppressive therapy and lack an HLA identical family member, our objectives are to make an initial assessment of the safety and efficacy of allogenic stem cell transplantation from either a matched unrelated donor or a mismatched reacted donor using the conditioning regimen of Cytoxan, reduced total body irradiation (TBI) and Campath IH. The principle measures of safety and efficacy will be :