Objective: To compare the values of preinduction transvaginal cervical length measurements and Bishop score to predict successful labor induction. Methods: A prospective, observational. trial of nulliparous women undergoing tabor induction. Inclusion criteria were gestational age between 36 and 42 weeks, singleton cephalic presentation of the fetus, and intact membranes. Preinduction cervical ripening was performed using 25 mu g intravaginal misoprostol (PGE1), repeated every 4 h, up to a maximum of 3 doses. Induction was subsequently continued by oxytocin and amniotomy. Results: A total of 43 women met the inclusion criteria. Mean preinduction cervical length for women with successful or failed tabor induction was 26 mm (95% Confidence interval [CI], 27-32) and 34 mm (95% CI, 33-38), respectively (P=0.002). Mean Bishop scores for successful and failed induction groups were 5.4 (95% CI, 5.2-6.2) and 3.1 (95% CI, 2.8-3.5), respectively (P=0.003). Conclusion: Digital examination and transvaginal ultrasound of the cervix predict successful tabor induction with reasonable accuracy. (c) 2007 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.