1. Patients with impaired bone marrow reserve, as indicated by one or more of the following: Prior myeloablative therapies with autologous bone marrow transplantation (ABMT) or peripheral blood stem cell (PBSC) rescue Platelet count < 100,000 cells/mm3 Hypocellular bone marrow Marked reduction in bone marrow precursors of one or more cell lines (granulocytic, megakaryocytic, erythroid) History of failed stem cell collection of > 4*106 CD34+/kg