A Japan-Korea cooperative survey on Takayasu arteritis has shown some differences in the features between Japanese and Korean patients with this disease. In angiographic findings, Japanese patients more frequently had lesions at the aortic arch and/or its branches (58% of 75 cases), while, in Korean patients, the abdominal aorta is the site of relatively frequent lesions (30% of 112 cases). Higher occurrence ofHLA-Bw52 was found in Japanese patients in comparison with Korean patients (46% vs 15%). The presence ofHLA-Bw52, however, might have a close association with Takayasu arteritis in Korea as well as in Japan. The complications in 126 Japanese and 88 Korean patients were also compared. The complications occurring with higher frequency in Japanese patients were aortic regurgitation, ischemic heart disease, and visual disturbances, while, in Korean patients, the more frequent complications were renovascular hypertension as well as hypertension of some other etiology.