OBJECTIVE: To explore changes of the serum granulocyte colony-stimulating factor (G-CSF) in children with acute respiratory airway infection. METHODS: Venous blood was obtained from 30 normal children, 189 children with acute respiratory airway infection without treatment and 50 children (from the group of 189 children) treated with antibiotics for 5～7 days. G-CSF levels were determined using the double antibody sandwich enzymelinked immunosorbent assay (PAS ELISA) and C reaction protein (CRP) levels were assayed using singleradial immunodiffusion. RESULTS: Of the 189 patients with acute respiratory airway infection, 105 were positive for G-CSF and 68 were positive for CRP (>12 ug/ml). Both G-CSF and CRP were positive in 23.8% of the patients. After a 5～7 day treatment course, the CRP of 50 turned from positive to negative and the G-CSF of 16 remained positive. CONCLUSIONS: Serum G-CSF levels increase in the stage of acute infection.