A series of 12 patients with angiographically proven arteriovenous fistula of the dura mater are reported. This condition is more common than might be supposed and should be considered whenever a patient complains of pulsatile tinnitus accompanied by an auscultatory bruit. Doppler sonography is the noninvasive method of choice in arriving at a precise diagnosis and guiding neurological and radiological investigations towards selective angiography of the external carotid artery, the only technique which will reveal the origin of the pedicles. Doppler sonography is also very useful in monitoring the course of the untreated disease and its postoperative course. Although these fistulae may remain asymptomatic for a long time, depending upon their drainage and localization, they may give rise to serious complications, in particular haemorrhage, which render in general surgical treatment desirable. With regard to pathogenesis, the fistulae may be congenital, but are most frequently acquired.