Allogeneic blood stem cell (BSC) transplantation has been performed experimentally in some patients with success. Wider application of this therapeutic modality has been hampered ultimately by many factors, mainly the concern that infusion of large numbers of donor T cells could result in an increased incidence and severity of graft-versus-host disease (GVHD). We report the short-term results of 17 allogeneic BSC transplants in patients with hematologic malignancies. When compared to standard BMT results, BSC transplants showed the advantages of faster engraftment, shorter hospital stay and fewer antibiotic needs. The incidence and severity of GVHD, as well as the general BMT-associated morbidity, was comparable between the two groups. BSC collection by apheresis was well tolerated and associated with less morbidity for donors, probably reducing the cost of the treatment. The collection of BSC was a single apheresis procedure and yielded adequate numbers of stem cells to ensure engraftment. Although this was not a prospective randomized study, the data obtained are encouraging and warrant more prospective and controlled studies.