['Chronic changes in flow rate through arteries produce adjustment of arterial diameters. We compared the relationship between flow velocity and diameter in the carotid and in the vertebral arteries of stroke patients.', "Using triplex ultrasonography, the internal diameter and flow velocities of the common carotid, internal carotid, and vertebral arteries of 176 consecutive stroke patients were measured. Correlations were examined with Pearson's statistics at an alpha level of 0.05.", 'Mean age of the patients was 59.3\u2009±\u200912 years, and 66% had cerebral infarcts. Diameter and blood flow velocities showed significant negative correlations (-0.115\u2009≥\u2009r\u2009≥\u2009-0.382) in the carotid arteries on both sides, but positive correlations (0.211\u2009≤\u2009r\u2009≤\u20090.320) in the vertebral arteries, even after controlling for age, gender, and blood pressure.'] Does the relationship of flow velocities to vessel diameters differ between extracranial carotid and vertebral arteries of stroke patients?