Objective: The purpose of this study was to determine if granulocyte colony‐stimulating factor (G‐CSF) is normally present in amniotic fluid and then to determine if amniotic‐fluid G‐CSF levels are affected by labor and intrauterine infection.Methods: Amniotic fluid was collected from 35 patients in 4 groups: no labor, early labor, late labor, and labor plus chorioamnionitis. G‐CSF levels were measured by enzyme‐linked immunosorbent assay (ELISA).Results: The mean amniotic‐fluid G‐CSF concentrations prior to labor were lower than during labor (0.49 ± 0.25 ng/ml for prior to labor vs. 1.83 ± 1.0 ng/ml for labor, P < 0.001). With chorioamnionitis, the mean levels were elevated compared with normal labor (25.0 ± 4.8 ng/ml for chorioamnionitis vs. 1.83 ± 1.0 ng/ml for normal labor, P < 0.0001). In early and late labor, G‐CSF was higher than prior to labor (0.49 ± 0.25 ng/ml for no labor vs. 1.48 ± 1.0 ng/ml for early labor, P < 0.02, vs. 2.2 ± 0.8 ng/ml for late labor, P < 0.0005). The mean concentrations in early and late labor were not different.Conclusions: G‐CSF is present in amniotic fluid and increased with labor. When labor is complicated by chorioamnionitis, G‐CSF is significantly elevated.