Sixty-five patients with nonvertex presentations at term were evaluated by ultrasonography to determine which factors were associated with a successful external cephalic version. Amniotic fluid volume, placental localization, type of breech, position of the fetal spine, and whether the breech had descended were determined and analyzed by chi 2 analysis. Only a frank breech and an anteriorly located fetal spine were associated with a successful version. Four episodes of fetal bradycardia occurred, none requiring operative intervention. There were no episodes of maternal bleeding or dislodgement of the placenta. Fifty-eight percent of all breech presentations were converted and 62% were delivered vaginally. We conclude that ultrasonography is useful in the evaluation of patients with a nonvertex presentation at term and can be used to predict which patients are likely to undergo a successful external cephalic version.