Although the cure of acute leukaemia has improved significantly, many patients will still relapse and die. The unraveling of the molecular pathogenesis of acute leukaemia has lead to the identification of new prognostic factors and improved the detection of minimal residual disease. The treatment of relapsed acute leukaemia with chemotherapy remains unsatisfactory. Allogeneic or autologous blood and marrow transplant (BMT) can cure a subset of patients with relapsed acute leukaemia. The identification of the graft-vs-leukaemia (GVL) effect has lead to the development of donor lymphocyte infusions to re-induce remission in patients with relapsed leukaemia after allogeneic BMT and also stimulated the development of the less toxic nonmyeloablative allogeneic transplant approach. The identification of molecular targets of therapy and the development of monoclonal antibody-directed therapy has generated optimism. It is possible that combinations of chemotherapy, molecularly directed therapy, and immunotherapy may be combined to cure an increasing proportion of patients with acute leukaemia.