We describe two families with Adams-Oliver syndrome (AOS), an autosomal dominant malformation syndrome (MIM No. 10030), in which cardiovascular malformations (CVMs) have been reported previously. In the first family, twin boys and their mother had the typical digital and scalp defects of AOS with various obstructive CVMs of the left heart (bicuspid aortic valve, Shone's complex). At least three other relatives not examined personally are reported to have related CVMs (aortic valve stenosis, hypoplastic left heart syndrome). In the second family, a girl had typical AOS digital and scalp defects and a bicuspid aortic valve. At least three other relatives are reported to be mildly affected. Tetralogy of Fallot had been previously reported as the most common CVM in AOS [Zapata HH, Sletten LJ, Pierport MEM (1995). J Med Genet 47:80-84.]. However, with the addition of these new patients and two other literature reports, we emphasize that approximately 20% have a CVM, frequently obstructive lesions of the left heart. Cardiology consultation should be offered to most patients with AOS.