Thirteen children and young adults with coarctation of the aorta as their principal cardiovascular abnormality, 11 with bicuspid aortic valves, were evaluated by orifice-view aortography to evaluate their aortic valvular morphology. For comparison 30 individuals with aortic valvular deformities but without coarctation of the aorta were similarly studied. Two distinct forms of bicuspid valves could be identified characterized by either the appearance of gross inequality of size of the two valve leaflets or an appearance wherein each leaflet closely approximated the size of the other, thus equally bicuspid. Excepting two individuals with normal, tricuspid, aortic valves, all of the patients with coarctation of the aorta had equally bicuspid aortic valves which contrasted to the group without coarctation in which the unequally bicuspid type predominated. This difference in bicuspid aortic valve morphology associated with coarctation of the aorta suggests a different developmental process involving the aortic valve as opposed to the situation in individuals without coarctation.