Direct and indirect arteriovenous fistulas were applied to the cervical vessels of 19 rats in order to study the haemodynamic parameters of angioma-like, rapid blood flow in small vessels. Flow was measured electromagnetically and intraoperatively using the Doppler sonography, and both methods were compared. Resultant alterations in vessel walls were examined under the electron microscope. Following fistula application, the flow rates increased by a factor of ten. At the same time, the flow pattern profile and stream resistance also changed. At present, the Doppler sonography device employed here is the only one commercially available, yet it could not detect rapid flow rates (greater than 85 cm/sec). The abnormal haemodynamic strain on the venous walls led to morphologically and angiographically detectable alterations.