. Patients were excluded if the breech was not mobile or if they had any contraindications to tocolysis or external cephalic version. After randomization 283 patients received either ritodrine (111 micrograms/min) or identical placebo by intravenous infusion for>or = 20 minutes. Up to three attempts at external cephalic version under ultrasonographic surveillance were performed. With an alpha error of 0.05 and a beta of 0.2, 264 patients were required to complete this study.