Acquired aplastic anaemia (AA) is a rare serious condition, characterized by bone marrow aplasia and peripheral blood pancytopenia. More than 75 % adult patients with severe AA are becoming long-term survivors if diagnosed early and treated appropriately. First-line treatment approaches in severe AA include immunosuppressive therapy or sibling haematopoietic stem cell transplantation (HSCT). For patients with acquired severe AA, the choice of treatment depends principally on the patient´s age and the availability of a matched donor. Best transplant strategies in sibling HSCT have been defined. The outcomes of allogeneic HSCTs in severe AA have significantly improved in the past decade, particularly in the unrelated donor setting, to such an extent that treatment strategies may be affected. Barriers to the use of unrelated-donor HSCT for severe AA include identifying a suitable alternative donor, and risks of graft failure, regimen-related toxicity, and graft-versus-host disease. A short interval between diagnosis and treatment will improve results of HSCT; therefore these patients should be referred to an experienced centre immediately.