The administration of hematopoietic growth factors after autologous peripheral stem cell transplantation is still controversial. In this prospective, randomized trial we aimed to investigate the impact of GM-CSF after the transplantation with G-CSF mobilized peripheral blood stem cells with respect to hematological engraftment and supportive therapy requirements. Thirty-one patients with solid and hematological malignancies were randomized in one group (n=16) receiving GM-CSF (Molgramostim, Leucomax; Sandoz- Schering-Plough Laboratories, Paris, France) from day 7 post transplant until neutrophil recovery (absolute neutrophil count >0.5x10⁹/L on three consecutive days) or in another group (n=15) receiving no GM-CSF. All patients received total CD34+ cells more than 2x10⁶/kg. The patients in both groups were comparable for age, sex, time between diagnosis and transplantation, total numbers of pretransplant chemotherapy regimens, previous radiotherapy, tumor type (solid or hematological) and numbers of total CD34+ cells infused. There was no difference between cytokine and nocytokine group with respect to leukocyte engraftment (11.9±2.2 vs. 11.9±2.9 days, respectively; p=0.936), platelet engraftment (12.6±3.6 vs. 11.9±3.9 days, respectively; p=0.691), number of days with parenteral antibiotherapy (10.8±4.7 vs. 11.9±3.7 days, respectively; p=0.662), number of days with fever over 38.1 °C (6.3±4.3 vs. 5.0±3.0 days, respectively; p=0.551), the use of red cells (2.6±1.7 vs. 2.9±1.0 units, respectively; p=0.623), the use of platelet transfusions (1.2±1.0 vs. 1.3±1.0 units, respectively; p=0.773), duration of posttransplant hospitalization (13.1±2.7 vs. 13.5±2.6 days, respectively; p=0.435). This randomized trial suggested that the administration of GM-CSF from day 7 until engraftment after autologous peripheral blood stem cell transplantation did not add any evident clinical benefit in terms of engraftment duration and supportive therapy requirements. [Turk J Cancer 2006;36(2):57-63].