OBJECTIVES: I. Compare the disease free survival of patients with leukemia, myelodysplasia, or lymphoblastic lymphoma after treatment with conventional (non-T cell depleted) or T cell depleted unrelated donor bone marrow transplantation. II. Compare the incidence of primary and secondary graft failure, acute and chronic graft-vs-host disease, complications (infection, veno-occlusive disease, interstitial pneumonitis), and relapse in these patients after these treatments. III. Compare the incidence of other malignancies, lymphoproliferative disorders, and post-transplant myelodysplasia in these patients after these treatments.