Unrelated bone marrow transplantation (BMT) is a major therapeutic option for patients with acquired severe aplastic anemia (AA): Improved survival has been achieved, thanks to better donor selection, conditioning regimens, and graft versus host disease prophylaxis, together with improved supportive care, including the diagnosis and treatment of opportunistic infections. We will discuss transplantation platforms, as used in unrelated donor transplants, and we will analyze major advances of the past years, including changes in the conditioning regimen and graft versus host disease (GvHD) prophylaxis. These changes extend the option of a bone marrow transplant for patients who lack an HLA-identical sibling and appear to improve engraftment and reduce graft versus host disease; whether this will be true for all age groups is currently being investigated.