Three cases of patients with quadricuspid aortic valve diagnosed with transthoracic echocardiography are presented. Two dimensional and color Doppler echocardiography are very useful for the diagnosis of quadricuspid aortic valve. According to the types of quadricuspid aortic valve classified by the size of four cusps identified by parasternal short axis view, therapeutic plan and prognosis of different types of quadricuspid valve will be varied. Echocardiographic demonstration of quadricuspid aortic valve widens the spectrum of aortic valve diseases especially if the cause of aortic regurgitation will not be defined clearly.