This study was designed to understand the uterine activity (UA) in normal labor. 43 nulliparous women(33 in normal course of labor and 10 in abnormal course of labor) were in the active phase of spontaneous labor with cephalic presentation for vaginal delivery. An open-end fluid filled intrauterine catheter connected to a pressure transducer was used to measure the uterine contraction intensity, frequency and duration. UA was quantified by means of Montevideo Unit (MU) and Uterine activity integral(UAI). The receiver operator characteristic(ROC) curve defined the cut-off points of UA between normal labor and abnormal labor. The results showed that MU and UAI were correlated with the rate of cervial dilatation in the active phase of labor (r = 0.3734 and 0.3502 respectively, P < 0.05). There was a strong correlation between MU and UAI (r = 0.7173, P < 0.001). The mean of UA in normal labor as MU = 226(s = 68.45) mmHg/15 min. UAI = 901(s = 258.02) kPa/15 min. The minimum of UA to normal labor in MU was 170 mmHg/15 min, of UAI 650 kPa/15 min. The study suggests that quantification of UA is very useful in the management of labor, especially in the proper use of oxytocin in cases abnormal labor.