Cardiac rhabdomyomas are the moil common primary tumor in infancy and childhood and are frequently associated with tuberous sclerosis. Although spontaneous regression of cardiac rhabdomyoma has been reported, prognosis of this tumor associated with subaortic stenosis is still considered to be poor and surgery continues to be indicated. A 4-day-old female was admitted due to tachypnea and cyanosis. Single rhabdomyoma arising from the interventricular septum associated with severe subaortic stcnosls as partially removed under cardiopulmonary bypass. Excised tumor sizc was 0.7$ imes$0.9$ imes$0.4cm in dimension. The postoperative course was uneventful and the infant discharged on the 14th postoperative day.