Objectives To determine the predictive effect of the transvaginal ultrasonographic cervical measurement in induction of labor among the nulliparous. Methods This prospective observational study recruited women with singleton gestation scheduled for induction of labor at ≥37 weeks. All the pregnancy women were nulliparous. Transvaginal ultrasonographic cervical measurement was performed and Bishop score was detemined, each by operators masked to the other measurement. Data were collected on parity, gestational age, mode of delivery, induction agent, induction onset of labor interval, Bishop score and cervical measurement. Results A total 121 women were included. A stepwise regression model identified cervical length was the best linear predictor of induction to onset of labor interval. ( r=0.67, P