Transplantation of blood-derived stem cells is increasingly performed because when used alone or when combined with autologous bone marrow grafting, it can demonstrably shorten myelosuppression following multi-agent chemotherapy. Hematopoietic growth factors can mobilize peripheral blood stem cells from the bone marrow to therapeutically intervene in accelerating hematologic recovery. Interleukin 3 (IL-3), whose hematopoietic activities were first described some ten years ago, is one of several candidate growth factors that may prove useful in enhancing this mobilization in order to obtain adequate yields of circulating stem cells for transplantation. IL-3 used in conjunction with synergistically acting cytokines such as granulocyte-macrophage colony stimulating factor (GM-CSF) or granulocyte CSF (G-CSF) have already yielded interesting results, while new factors like stem cell factor are in the process of clinical evaluations and appear promising. However, further issues remain to be clarified to confirm the general applicability of cytokine-augmented peripheral blood stem cells in improving on-schedule delivery of high-dose myelosuppressive chemotherapy in patients with malignancies.