Peripheral blood stem cells (PBSCs) collected following stimulation with filgrastim are commonly used for autologous hematopoietic transplants. PBSCs are also now being used for some syngeneic and allogeneic hematopoietic transplants involving HLA-matched sibling donors. However, many issues remain unanswered about the use of PBSCs for allogeneic transplants and the effects of filgrastim on healthy individuals. The purpose of this study is to determine the effectiveness of filgrastim stimulated PBSCs in hematopoietic cell transplants involving unrelated donors and to determine the effects of this donation process on unrelated stem cell donors.