This randomised controlled study compared the efficacy of double-balloon catheter versus vaginal prostaglandin E2 (dinoprostone) for induction of labour. In total, 825 pregnant women with cephalic presentation and an unfavourable cervix undergoing induction for conventional indications were randomised to double-balloon or vaginal dinoprostone (3 mg) groups. There was a significantly higher failure rate for labour induction in the balloon group (relative risk: 1.25, 95% confidence interval [CI]: 1.02-1.49). Median induction time was 27.3 h in the balloon group and 29.8 h in the dinoprostone group (difference not significant). After 24 h, 55.3% had given birth in the balloon group versus 54.3% in the dinoprostone group. Additional oxytocin stimulation was used more often in the balloon (46%) compared with that in the dinoprostone (34%) (relative risk: 1.34 (95%CI 1.16 -1.54) group. Caesarean section rates and neonatal outcome were similar. Overall, the two methods for induction were comparable with regard to efficacy and safety.