To better define the clinical significance of vertebrobasilar dolichoectasia, the clinical signs and symptoms and basilar artery parameters of diameter, height, and transverse position were evaluated in two groups of symptomatic patients. Ten patients had isolated involvement of the third, sixth, or seventh cranial nerves. The other 10 patients had multiple neurologic deficits including combinations of compressive cranial nerve deficits, both ischemic and compressive central nervous system deficits, and hydrocephalus. Although significant differences for mean basilar artery diameter and height exist between these two groups, the symptomatology and basilar artery parameters present as a spectrum. A symptomatic patient with a normal-caliber, but tortuous, basilar artery is more likely to have isolated cranial nerve involvement. Conversely, the patient with marked basilar artery dilatation (ectasia) is far more likely to present with multiple compressive or ischemic neurologic deficits. Conventional angiography in patients with dilated basilar arteries carries a significant risk for brainstem ischemia. Most authors agree that when vertebrobasilar dolichoectasia has been demonstrated by computed tomography, additional angiography, if required at all, should be performed by digital subtraction techniques.