Thallium-201 myocardial imaging was performed in 150 patients with a history of Kawasaki disease, aged 6 months to 16 years old. Forty-five patients were studied with ergometer exercise and 105 patients had dipyridamole administration. The findings of thallium imaging were compared with those of coronary angiography. Seventy-two cases with severe coronary stenosis (over 75%) were classified in 3 groups; 13 with the left anterior descending artery lesion, 31 with only the right coronary artery lesion and 28 with multi-vessel involvement. In 72 cases with severe coronary stenosis, the sensitivity of thallium imaging for detecting coronary stenotic lesions was 85%, 74% and 67% in the 3 groups, respectively. In 78 cases without severe coronary stenosis, 5 cases (6%) had persistent perfusion defects on thallium imaging, 3 of which were associated with dyskinesis of the left ventricle documented by cineangiography. They were considered to have damaged myocardium probably due to peripheral myocardial infarction or myocarditic problems. Thallium-201 myocardial imaging was proved to be a useful method to detect coronary stenosis, however its sensitivity for detecting lesions of the right coronary artery or multi-vessels was relatively low. This may be attributable to a significantly higher incidence of segmental stenosis (recanalization) with sufficient coronary flow and multiple coronary collateral vessels in patients with such lesions.