The immunological graft-versus-leukemia (GVL) effect seen after allogeneic stem cell transplantation suggests that stimulating the patient's own T cell responses to MDS and leukemia with a vaccine might also retard disease progression and even achieve disease remissions. WT1 and PR1 were identified as target antigens because both antigens are highly expressed by CD34+ stem cells of most patients with myeloid malignancies but not by normal marrow cells. An immunotherapeutic approach to vaccinate against PR1 and WT1 antigens could induce T cell response against MDS and leukemic cells while sparing normal cells and by using a combination of two antigens the risk of disease escape by antigen down regulation should be further diminished.