A 49-year-old woman presenting with leg edema and progressive dyspnea on exertion was found to have a diastolic murmur. Echocardiography revealed increased left ventricular volume and severe aortic regurgitation (AR). She also had pain in her chest and left shoulder. Gallium scintigraphy showed increased uptake in the sternum, and further examination indicated chronic osteomyelitis in the sternum and the proximal portion of bilateral clavicles. Aortic valve replacement was performed and the ascending aorta was found to have inflammatory wall thickening with adhesion formation. Histological study and other postoperative examinations revealed Takayasu's arteritis (TA). Involvement of bone is rarely described in TA, and typical manifestations such as claudication of extremities, decreased brachial artery pulse, and arteriogram abnormality were absent, which made the preoperative diagnosis difficult. Here we report a case of severe AR due to TA which presented much difficulty in the diagnosing process, because a rare complicated illness, osteomyelitis was clinically apparent and there were few clinical manifestations related to TA.