We report a case of a 64 year-old woman who had a quadricuspid aortic valve associated with aortic regurgitation of mild degree diagnosed by transesophageal echocardiography (TEE). The four cuspids were of the same size. This valve anomaly could not be diagnosed by transthoracic echocardiogram (TTE). The TEE is a diagnostic noninvasive procedure that gives the best information in quadricuspid aortic valve malformation.