After informed consent, 86 patients with advanced cancer undergoing potentially myelosuppressive cytotoxic chemotherapy were randomized to receive placebo or subcutaneous granulocyte-colony stimulating factor (G-CSF) 5 micrograms/Kg/day in order to prevent severe neutropenia and its related morbidity. The incidence of neutropenia (absolute neutrophil count < 1,000/mm3) was significantly reduced in patients receiving G-CSF than in controls (18% versus 42%; P < 0.05). The duration of neutropenia was also shortened by the administration of G-CSF (4.8 versus 8.2 days; P < 0.05). Therapy with G-CSF has also a positive impact on the dose-intensity of employed regimens. Patients treated with G-CSF showed oral fungal disease in 9% of cases, while control patients had a 21% incidence (NS). Patients treated with G-CSF received 91% of the programmed dose-intensity as compared to 71% of control patients (P < 0.05). These data strengthen the clinical usefulness of G-CSF in the prevention of chemotherapy-related neutropenia, infections, and reduction in dose-intensity. Further studies are required to establish if the increase in dose-intensity allowed by G-CSF treatment may positively influence the outcome of cancer patients.