Eleven of twenty-four patients with severe aplastic anemia given marrow grafts from HLA-identical siblings between October 1970 and March 1973 are alive with normal marrow function and continued evidence of engraftment 3-5 yr later. Ten have been leading normal lives with no immunosuppressive or other drug therapy since day 100 postgrafting. One has had chronic graft-versus-host disease of the skin which is now slowly improving with no therapy. He returned to full-time employment in the summer of 1975. The long-term well-being of almost half of our initial patients emphasizes the importance of marrow transplantation for the treatment of severe aplastic anemia.