Among 131 patients with Kawasaki disease who underwent cardiac examinations from December 1979 to July 1984, six (4.6%) had aortic regurgitation documented on aortography. A protodiastolic murmur typical of aortic regurgitation was heard in four patients. Both cardiac enlargement on chest roentgenogram and ECG signs of left ventricular hypertrophy were demonstrated in only half of the patients. Of five patients who underwent a second angiographic study 1 year later, two no longer had aortic regurgitation; pulsed Doppled echocardiography at this point revealed aortic regurgitant flow in the remaining three patients. All patients had associated coronary artery aneurysms, and two patients developed subsequent myocardial infarction. The development of aortic regurgitation following Kawasaki disease has been considered to be causally related to the carditis that most frequently occurs during the acute stage of the illness. Our data indicate that aortic regurgitation is not rare but is an important additional cardiovascular complication of Kawasaki disease.