From September 1976 to August 1988, 205 patients with mucocutaneous lymph node syndrome (Kawasaki disease) were evaluated; 29 were suspected of having coronary artery abnormalities because of either abnormalities on echocardiography (n = 21), congestive heart failure (n = 3), prolonged fever (n = 3) or cardiac arrest (n = 2). All 29 underwent cardiac catheterization and 22 were found to have coronary artery abnormalities. An additional 4 patients were diagnosed solely by autopsy; therefore, 26 patients (12%) in this series had coronary artery abnormalities. The clearance of contrast medium from the coronary arteries after aortography was significantly prolonged in patients with coronary artery aneurysms as compared with that in a control group (p less than 0.001). All patients exhibited delayed clearance of contrast medium on the initial aortogram as compared with that on follow-up studies (p less than 0.01). Of the 22 patients with angiographically documented coronary artery abnormalities, 19 had right and 20 had left coronary artery involvement; the majority had diffuse involvement of both vessels. In 15 patients who underwent follow-up catheterization 6 months to 7 years after initial study, complete resolution was observed in only 37% of affected coronary artery segments. In four patients, three of whom were asymptomatic, severely stenotic or occluded coronary artery segments were found on late catheterization. Coronary artery bypass surgery was performed in two of these patients. Echocardiography did not detect any of these stenoses. Although echocardiography is important for initial diagnosis and serial evaluation, angiography is essential to fully define the nature and extent of coronary artery lesions, particularly if stenosis is present.