The authors evaluated the distensibility of the coronary arterial wall by pharmacoangiography with intravenous administration of dipyridamole in 38 patients with Kawasaki disease. In the acute stage of the illness, the coronary arteries were evaluated for aneurysms by two-dimensional echocardiography. After the acute stage of the illness, selective coronary cineangiographies were performed by Seldinger's method under general anesthesia before and after intravenous administration of 0.6 mg/kg of dipyridamole for four minutes. The calibers of aneurysms and normal appearing segments of coronary arteries, at most 7 segments in 1 patient, were measured before and after dipyridamole administration on the high-quality cineangioanalyzer and percentages of coronary arterial dilatation were calculated. In 14 cases without evidence of coronary arterial lesions, the distensibility was 10.2 +/- 4.7% (mean +/- SD). The distensibility of 32 aneurysms in 16 cases was 0.6 +/- 1.1% and was significantly decreased (p less than 0.001). In 24 cases with coronary arterial lesions, aneurysms, stenosis, or obstruction, the distensibility of normal appearing segments of coronary arteries was 4.5 +/- 4.9% and was significantly decreased (p less than 0.001). This method is useful in evaluating distensibility and appears to be effective in detecting pathologic changes of the coronary arterial wall, even if it appears normal in shape. The patient with previously diseased coronary arteries should be kept under careful longterm surveillance.