Objective. To evaluate the efficacy of prostaglandin E2 (PGE2) for cervical ripening at preterm and to identify factors predicting ripening failure. Design. A retrospective study of women admitted for preinduction cervical ripening with PGE2 vaginal tablets at preterm (n=444). PGE2 vaginal tablets were administered at 6-8 h intervals until cervical ripening was achieved (Bishop score ≥7) or ripening failed (Bishop score <7 after administration of 4 PGE2 tablets). Data were compared with a control group of women admitted for preinduction cervical ripening with PGE2 vaginal tablets at term (n=1,029). A multivariate logistic regression analysis was performed to detect factors predicting ripening failure. Results. Women at preterm required a significantly higher number of PGE2 tablets compared to women at term (2.0±1.1 versus 1.6±0.9, p<0.001). Overall rates of ripening failure and caesarean section due to failed induction were significantly higher in preterm than term gestations (11.4 versus 1.1% and 9.7 versus 0.4%, p<0.001), and were inversely related to gestational age. Nulliparity, lower gestational age at delivery, lack of cervical dilatation, and higher maternal age were significant predictors of ripening failure at preterm. Conclusion. The use of PGE2 for preinduction cervical ripening at preterm may be associated with an increased risk of ripening failure and caesarean section compared with term gestations. This information may be useful when consulting women regarding the available options when premature delivery is necessary.