Objective, To compare the effectiveness of the oxytocin receptor antagonist atosiban with the beta mimetic fenoterol as uterine relaxants in women undergoing external cephalic version, ECV, for breech presentation. Design, Multicentre, open label, randomised controlled trial. Setting, Eight hospitals in the Netherlands, August, to May, . Participants, women with a singleton fetus in breech presentation and a gestational age of more than, weeks were randomly allocated in a, ratio to either, ., mg atosiban, n, or, μg fenoterol, n, intravenously for uterine relaxation before ECV. Main outcome measures, The primary outcome measures were a fetus in cephalic position, minutes after the procedure and cephalic presentation at delivery. Secondary outcome measures were mode of delivery, incidence of fetal and maternal complications, and drug related adverse events. All analyses were done on an intention-to-treat basis. Results, Cephalic position, minutes after ECV occurred significantly less in the atosiban group than in the fenoterol group, v, relative risk, ., confidence interval, ., to, ., . Presentation at birth was cephalic in, n, of the atosiban group and, n, of the fenoterol group, ., ., to, ., and caesarean delivery was performed in, n, of women in the atosiban group and, n, in the fenoterol group, ., ., to, ., . No significant differences were found in neonatal outcomes or drug related adverse events. Conclusions, In women undergoing ECV for breech presentation, uterine relaxation with fenoterol increases the rate of cephalic presentation, minutes after the procedure. No statistically significant difference was found for cephalic presentation at delivery. ; Joost Velzel, Floortje Vlemmix, Brent C Opmeer, Jan F M Molkenboer, Corine J Verhoeven, Mariëlle G van Pampus, Dimitri N M Papatsonis, Joke M J Bais, Karlijn C Vollebregt, Liesbeth van der Esch, Joris A M Van der Post, Ben Willem Mol, Marjolein Kok