In a patient with active extracranial giant cell arteritis, duplex ultrasonography demonstrated hypoechoic mural thickening of the brachial, axillary, subclavian, and carotid arteries with bilateral subtotal occlusions of the brachial and axillary arteries. The ultrasound image of the artery walls became midechoic within 8 weeks, and hyperechoic within one year after start of treatment with corticosteroids. A similar hypoechoic mural thickening of the temporal arteries has been recently described in active giant cell arteritis. The dark ultrasound image is due to an edema of the vessel wall in the acute stage. The brighter ultrasound image might be due to fibrosis in the chronic stage of the disease.