This report describes a case of right coronary sinus of Valsalva aneurysm which ruptured into the left ventricle. The diagnosis was made with two-dimensional transthoracic echocardiography which showed an abnormal structure extending from the aortic root into the left ventricle adjacent to the interventricular septum. Subsequent examinations with transesophageal echocardiography and aortic root angiography and surgical findings confirmed the diagnosis of transthoracic echocardiography. The patient underwent aortic valve replacement. At follow-up 12 months later, the patient was without symptoms and repeated echocardiographic examinations showed no recurrence.