Quadricuspid aortic valves (QAVs) is a rare congenital malformation. We report two cases of QAV associated with aortic regurgitation. The one is incidentally diagnosed and uncomplicated, and the other is symptomatic and associated with infective endocarditis. In most cases, QAVs are associated with valve regurgitation, with a concurrent stenosis in some patients, while only a small number of QAVs are functionally normal. Once the diagnosis has been made, echocardiographic follow-up is recommended, because of progression to severe valve regurgitation and the risk of infective endocarditis.