A pair of conjoined twins (thoracopagus) was delivered abdominally after antepartum diagnosis. Obstetrical planning is more likely to be successful with antepartum diagnosis, which can be done only if the possibility of conjoining is considered with each twin gestation. Once a twin gestation is suspected, ultrasonography should be performed for confirmation. Conjoined twins should be suspected in a gravid mother with multiple gestations and an abnormal fetal attitude. When the images cannot be separated on ultrasonography, amniographic examination, using a double contrast medium of oil-water, should demonstrate dye in the gastrointestinal tract and a union between the twins, as well as establish the presence of a monoamniotic sac. Because of increased fetal morbidity and mortality of vaginal delivery in monoamniotic twins, even if not conjoined, elective cesarean section at term will ensure the best chance for fetal survival.