Introduction. There are few studies about intravenous fentanyl infusion for reduce labor pain. This study evaluate the usefulness of intravenous fentanyl infusion for labor analgesia. Methods. Seventy seven healthy pregnant women were randomized to recive 1.5-2.5µg/kg/hr intravenous fentanyl infusion (interventional group) or placebo (control group). Maternal labor pain intensity, systolic, diastolic and mean arterial blood pressure, pulse and respiratory rate, frequency of nausea and vomiting were monitored. Fetal heart rate (FHR) and neonatal APGAR score also monitored. Results. Maternal intensity of labor pain, frequency of nausea and FHR changes were significantly lower in interventional group. There was no significant difference between groups about maternal frequency of vomiting, systolic, diastolic and mean arterial pressure, pulse rate and neonatal 1 and 5 min APGAR score. Discussion. Intravenous fentanyl infusion (1.5-2 µg/kg/hr) during active phase of labor can diminish labor pain without any side effects of neonate and mother.