We studied the thoracic aorta in 42 female patients with Takayasu arteritis by magnetic resonance imaging (MRI) with a 1.5-T superconducting instrument and compared the findings with those in 10 healthy female controls. Images in the transaxial and oblique sagittal planes were acquired by cardiac gating using a spin-echo pulse sequence. Images in the oblique plane were also obtained with cine MRI. Vascular changes were found in 41 (98%) of the patients. Dilatation of the ascending aorta was observed in 20 patients (48%), while stenotic changes were more characteristic in the descending aorta (16 patients, 38%). Moderate signal-intensity masses on the aortic wall were encountered in 21 patients (50%), suggesting mural thrombi. Turbulent blood flow was observed around all masses by cine MRI. HLA analysis revealed that patients carrying HLA-B52 typing showed these masses more frequently than those without this typing (P < 0.05). Cine MRI demonstrated aortic regurgitation in 20 patients (48%), all of whom showed dilated ascending aorta; furthermore, 14 (70%) of them were confirmed as carrying HLA-B52. Thus, MRI was a useful non-invasive tool not only for the evaluation of the morphological changes in the aorta and its branches, and of the hemodynamic disturbance in Takayasu arteritis, but also for follow-up of the morbid condition.