A set of dicephalous parapagus twins was born at 36 wk gestational age. Twin A had complex congenital heart disease in the form of a single ventricle that would be fatal without surgical intervention. Twin B had normal intracardiac anatomy. The twins were deemed surgically inseparable and the parents requested palliative open-heart surgery on Twin A. The twins shared a common circulatory system to the lower half of the body so that physiological manipulations in one twin adversely affected the other's hemodynamic condition. Twin A underwent successful single ventricle palliation; however, after a prolonged hospitalization, the infants died secondary to severe respiratory disease in Twin B.