Lipomatous hypertrophy of interartiral septum (LHIS) is a rare entity that is characterized by the excessive deposition of fat in the interatrial septum. The appearance of LHIS on echocardiogram is a bilobed or dumbbell-shaped in interatrial septum. We report a case of 56-years man with frequent premature ventricular contraction on holter monitoring which may related to his sudden cardiac death diagnosed lipomatous hypertrophy of interatrial septum by echocardiography.