Treatment of healthy donors with recombinant human granulocyte colony-stimulating factor (rhG-CSF) allows the mobilization and peripheralization into circulating blood of an adequate number of CD34+ cells that can then be collected by leukapheresis (PBSC). This procedure avoids the invasiveness of bone marrow harvest and the risks related to general anesthesia. The main adverse effects of rhG-CSF are: bone pain, 84%, headache, 54%, fatigue, 31%, and nausea, 13%, which are usually scored by the donors as moderate to severe, resolving within 2-3 days after discontinuation of the cytokine. Analgesics, mainly acetaminophen, are sufficient to control the pain. Less than 5% of the donors experience non-cardiac chest pain, a local reaction at the injection site, insomnia, dizziness or a low-grade fever. Discontinuation of the PBSC procedure because of adverse effects of rhG-CSF or leukapheresis is rarely necessary (0.5%) but this good tolerability can be hampered by the need, in 5-20% of cases, for an adequate venous access that requires insertion of a central or venous catheter. There are no absolute contraindications to the stimulation of healthy donors with rhG-CSF but the description of cases of non-traumatic splenic rupture, iritis, cardiac ischemia, and gouty arthritis suggests that further precautionary restrictions are advisable when deciding eligibility for PBSC collection. The main advantages for patients receiving an allogeneic PBSC transplant are the faster hematologic and immunologic recovery and the potential for a greater efficacy in advanced disease by lowering the transplant-related mortality. One of the major concerns regarding the use of rhG-CSF in unrelated healthy donors is the uncertainty about its possible role in triggering malignancy, in particular myelodysplastic syndrome and acute myeloid leukemia. There are no studies with an adequate sample size and follow-up that can answer this question but two recent retrospective studies reported that in the medium term rhG-CSF is not associated with an excess of lymphoproliferative disorders. Currently, caution on the long-term safety of the use of rhG-CSF in healthy donor is still warranted but the data so far accumulated on allogeneic PBSC transplants are encouraging both as far as concerns the good short-medium tolerability profile of G-CSF-stimulation of the donor and the potential major efficacy in leukemia patients.