During the past decade, investigators have evaluated the role of hematopoietic growth factors as cytokines that could potentiate the cytotoxic action of certain chemotherapeutic agents when administered simultaneously with induction therapy. Such cytokines included granulocyte-macrophage colony-stimulating factor, granulocyte colony-stimulating factor, interleukin 3, and stem cell factor. Phase I and II studies have confirmed a significant biologic activity of such priming therapy, and the aggregate of subsequent controlled studies have also established the safety of such manipulations. However, despite the plethora of clinical trials, data regarding clinical efficacy remain uncertain. It is fair to say that little progress in our clinical understanding has occurred during the past 24 months and at the present time, the concurrent use of growth factors with chemotherapy, as a method of enhancing the antileukemic action of cytotoxic therapy, remains very investigational.