Objectives-Takayasu arteritis is a relatively rare chronic nonspecific form of large-vessel vasculitis in which the involved vessels develop stenoses, occlusions, dilatations or aneurysms, and dissections. Dissections of the arteries in patients with Takayasu arteritis are not well understood. In this study, we explored the sonographic characterization of these rare complications secondary to Takayasu arteritis. Methods-We evaluated arterial dissections in 72 patients with a clinical diagnosis of Takayasu arteritis by vascular sonography and transthoracic echocardiography. We analyzed the dissection distribution and morphologic characteristics of the dissected intima/layer and lumen of the involved vessels. Results-Twelve of 72 patients had arterial dissections, in whom 16 dissected segments were identified. The involved arteries included the carotid, subclavian, vertebral, brachial, celiac, and femoral arteries, aortic arch, and abdominal aorta. The dissection lesions occurred at any age and coexisted with the aforementioned injuries. Evaluation of the dissected intima/layer and the involved lumen by sonography was technically complicated. The morphologic characteristics of the dissected intimae and involved lumens were complex, with most of the dissected intimae/layers having the characteristic "macaroni" sign in the arterial wall. High-frequency and high-resolution sonography, color Doppler flow imaging, and other techniques were useful in elucidating greater lesion details. Conclusions-Arterial dissections in Takayasu arteritis can involve any anatomic vessel location and have complex morphologic characteristics. Sonography is the optimal technique for diagnosis and follow-up of patients with Takayasu arteritis and dissections.