A comparative study of twin pregnancies with vertex-breech and vertex-vertex presentation was undertaken to evaluate the effect of mode of delivery on perinatal outcome. During the years 1978-1984 there were 89 cases of vertex-breech deliveries at our institution and a control group of 89 cases of vertex-vertex presentation were chosen. The cesarean section rate was 11.2% for both twins in vertex-breech, and 20.2% for the first twin and 23.6% for the second in vertex-vertex presentation. The primary indications for cesarean section were not related to the type of presentation. The perinatal mortality was 22.4/1000 in the study group and 89.8/1000 in the control population. There were no statistically significant differences in 5-min Apgar scores and perinatal morbidity between the two types of presentation. We found that the high perinatal morbidity and mortality of both twins is related to prematurity and intrauterine growth retardation and not associated with the type of presentation of the second twin. Therefore, routine cesarean section for vertex-breech presentation is not necessarily indicated.