[en] Purpose : To assess the efficacy of recombinant human granulocyte-macrophage colony-stimulating factor(GM-CSF) in the neutropenia by radiotherapy. Materials and Methods : Eleven patients with various solid tumor were treated with a daily subcutaneous dose of GM-CSF(3-7 microgram/kg) for 5 days during the radiotherapy. Before and during the course of the study all the patients were monitored by the recording of physical examination, the complete blood count with differential and reticulocyte count and liver function test. Eight patients received patients received prior or concurrent chemotherapy. Results : In 10 patients, the neutrophilic nadir was significantly elevated and the length of time that patients had a neutrophil count below 10³/mm³, a threshold known to be critical to acquiring infective complications was shortened following GM-CSF injection. A significant rise (two fold or greater) of neutrophil count was seen in 10 of 11 patients. In most patients, discontinuation of GM-CSF resulted in a prompt return of granulocyte counts toward baseline. However the neutrophil count remained elevated over 10³/mm³ during radiation therapy, and radiotherapy delays were avoided. Other peripheral blood components including monocytes and platelets also increased after GM-CSF treatment. No significant toxicity was encountered with subcutaneous GM-CSF treatment. Conclusion : GM-CSF was well tolerated by subcutaneous route and induced improvement in the neutropenia caused by radiotherapy