9 patients with severe aplastic anemia (SAA) were treated with bone marrow transplantation (BMT). 5 were conditioned with cyclophosphamide and received and HLA-identical graft (4 patients) or a mismatched graft (1 patient): 1 rejected the graft on day 30 and died on day 34 during conditioning for a second transplant; 1 died on day 15 with acute and severe graft versus host disease (GvHD) in the absence of haemopoietic engraftment; 3 are alive and complete chimeras at 1,069, 490 and 332 days after transplantation. GvHD developed in 4 patients and was treated successfully in 3 with high dose methylprednisolone and/or antilymphocytic globulin (ALG). 4 patients were conditioned with ALG and received bone marrow from a haploidentical sibling or parent: patient was refractory; 3 patients showed evidence of hematologic reconstitution, but of these required a second course of ALG. 3 patients in this group are alive between 60 and 490 days; 1 patient died on day 121 of HBSAg-negative acute hepatitis.