Human polymorphonuclear cells (PMN) and monocytes (MO) from four ovarian cancer patients and seventeen normal donors were in vitro pretreated with different concentrations (25, 50 and 100 IU, respectively) of rhGM-CSF. Phagocytosis and killing of PMN and MO as well as PMN polarization were evaluated in cancer patients before treatment (T0) and at the end of each chemotherapeutic cycle (T1, T2, T3 and T4, respectively) in comparison with normal donors. RhGM-CSF did not affect phagocytosis and killing of PMN and MO. On the other hand, this cytokine was per se endowed with the capacity to enhance PMN polarization in both cancer patients (at T2 interval) and normal donors.