In 50 healthy subjects the internal diameter of the intracranial vertebral artery were measured by echocolor doppler method. The diameter of left vertebral a. was greater than that of the right in most subjects (58%); the mean left/right difference was statistically significant (p < 0.05). Analyzing men and women separately, the difference remained significant only in women (p < 0.05). A significant correlation was found between vertebral a. diameter and sex (p < 0.01). The vertebral a. diameter had a tendency to increase with age, that reached significance only for the left vertebral one. No significant correlation was found between body surface area and vertebral a. diameter.