Two clinical results of peripheral blood stem cell support are commonly considered: (1) the effect on hematopoietic recovery and (2) the effect on the underlying malignancy. The dynamics of hematopoietic recovery after autologous bone marrow transplantation and after autologous peripheral blood stem cell transplantation in a clinical setting are similar if no exogenous cytokines are administered and the peripheral stem cells are collected while their numbers are not deliberately increased (mobilised). If mobilized peripheral stem cells are transplanted, hematopoietic recovery is accelerated. In some circumstances, patients who receive peripheral stem cell transplantation may experience an improved progression-free survival after high-dose therapy when compared with similar patients who receive autologous bone marrow transplantation. Explanations for such a survival advantage might include (1) a lower likelihood of occult tumor cells capable of restoring disease in peripheral stem cell autograft products than in bone marrow harvests, (2) a greater number of cytotoxic effector cells capable of destroying occult tumor cells in the peripheral stem cell collections than in bone marrow harvests, and (3) a different and advantageous pattern of immunologic recovery following autologous peripheral stem cell transplant compared to autologous bone marrow transplant.