Background Takayasu arteritis (TA) is a rare large-vessel arteritis that primarily affects the aorta and its major branches. The aim of this study was to describe the value of high frequency ultrasound for monitoring of inflammatory activity. Methods Twenty-five patients, range 11-71 years, diagnosed with TA were investigated with duplex ultrasound (DUS) including follow-up studies. Twenty-five healthy controls were also investigated. Nine patients had newly diagnosed active TA. Sixteen patients had stable/inactive disease at baseline DUS, and TA was diagnosed median 4 center dot 5 years previously. Intima-media thickness (IMT), vessel and lumen diameter were measured in the carotid arteries, central neck arteries and the aortic arch. The vessel walls were studied qualitatively. The Takayasu ultrasound index was created for inflammatory activity scoring. Results Intima-media thickness in common carotid artery (CCA) was (median and 25-75 percentile parenthetic) 2 center dot 3 mm (1 center dot 7-2 center dot 9) in clinically active TA, 1 center dot 2 mm (1 center dot 1-1 center dot 6) in clinically stable TA (Pamp;lt;0 center dot 001) and 0 center dot 5 mm (0 center dot 5-0 center dot 6) in healthy controls (Pamp;lt;0 center dot 001). Clinically active TA had prominent increase in IMT and/or increased vessel diameter, and/or intramural arteries, and/or hypoechogenic areas interpreted as oedema in the vessel wall. TA in clinical remission was characterized by increased IMT with medium to high echogenicity with or without fibrotic stripes. The Takayasu ultrasound index was higher in patients with active disease versus treated disease, 2 center dot 55 (1 center dot 60-3 center dot 05) versus 1 center dot 30 (1 center dot 00-1 center dot 58), (P = 0 center dot 003). Conclusion DUS is an excellent tool to monitor inflammatory changes in the vessel wall in TA. Further DUS studies in larger patient populations are warranted.