We measured the granulocyte-colony stimulating factor (G-CSF) levels in cord blood and peripheral blood obtained from full-term or pre-term infants during the first 3 days of birth. The mean G-CSF level among cord blood (17.2 pg/mL) was similar to that of peripheral blood on day 0 (18.3 pg/mL) and day 1 (13.6 pg/mL), while that of peripheral blood on day 0 was significantly higher than on day 2 (10.9 pg/mL) and day 3 (8.8 pg/mL; both P < 0.05). There was no correlation between neutrophil counts and G-CSF levels. No difference was found in neutrophil counts or G-CSF levels between infants who weighed more or less than 2500 g at birth. These results suggest that the neonatal neutrophil count depends on regulatory factors other than G-CSF.