During a 6-year-period, in 45 patients the diagnosis of dolichoectatic intracranial arteries was established. Dolichoectasia of the vertebrobasilar system was the most frequent finding (n = 39). Twenty-two patients presented with brain stem ischaemia, and 10 patients had ischaemic hemispheric events. Six patients had symptoms due to compression of cranial nerves. Hydrocephalus was observed once. Peak and mean flow velocities in 39 patients with dolichoectatic basilar arteries as revealed by transcranial Doppler ultrasound were significantly reduced (p less than 0.00001) when compared with an age-adjusted control group of 20 patients without evidence of vertebrobasilar dolichoectasia on angiogram. Non-invasive MR-angiography offered an excellent imaging of the vascular abnormality. The combined use of CT, TCD, MRI and MR-angiography allows reliable non-invasive diagnosis of dolichoectatic intracranial arteries. This condition seems to play an underestimated role in stroke patients, in particular with respect to the vertebrobasilar circulation.