In patients with subclavian steal (SS), the risk of stroke must be evaluated before angiographic assessment or surgery is performed. The criteria for the evaluation of stroke risk in these patients have not yet been established. SS is a hemodynamic phenomenon that sometimes produces no clinical symptoms and is sometimes associated with neurologic symptoms. Transcranial Doppler provides a noninvasive method of obtaining information on cerebral hemodynamics; this information can be useful in the pathophysiologic evaluation of stroke risk. Transcranial Doppler findings from 63 patients (28 asymptomatic) (mean age, 56.4 years) with SS collected over a 4-year period were classified on the basis of the levels of hemodynamic changes within the intracranial circulation. The Doppler study findings revealed a significant association (P < 0.01, by chi-square test) only with neurologic symptoms, demonstrating hemodynamic involvement of the carotid-basilar collateral pathways.