The present study was designed to confirm the use of GM-CSF, made by the Beijing United Biological Engineering Company, in leucocytopenia after chemotherapy in 12 patients with malignant tumor. In patients with malignant tumor the interval leucocytopenia needed shortened 5 days compared with that in control subjects. At the same time GM-CSF could be resistant to infection significantly, especially in patients with complicated infection, and the antibiotic applying time decreased. In addition, clinical experence had shown that there was no obvious side-effects in general dosage. Thus, these findings indicate that GM-CSF is a kind of essential drug in radical chemotherapy in patients with tumor.