By means of two dimensional echocardiography supravalvular aortic stenosis was diagnosed in two siblings and their cousin. Autosomal dominant transmission with incomplete penetrance or even non-penetrance is assumed to be involved. Somatic stigmatization, typical for Williams' syndrome, failed to be present in the affected children. The reported family provides further evidence that familial supravalvular aortic stenosis and Williams' syndrome are two distinct clinical entities. (Tab. 1, Fig. 3, Ref. 23.)