We investigated the patterns of vasomotion in various conduit arteries of the human arm. The internal diameter of the brachial, radial, ulnar, and digital artery was measured noninvasively in 17 healthy volunteers (aged 24-40 yr), using a high-precision ultrasonic echotracking device. Under resting conditions, the radial, ulnar, and digital internal diameter exhibited spontaneous oscillations (vasomotion) with a relative amplitude ranging from 1 to 5% of the mean diameter and a fundamental frequency ranging from 0.01 to 0.05 Hz. This oscillatory behavior was either quasi-periodic or irregular. The low-frequency mode (f < or = 0.05 Hz) present in the diameter signal was identified neither in the heart rate nor in the blood pressure signal. To determine whether the oscillatory activity was propagative, simultaneous measurements of diameter at two sites on the right radial artery were performed and revealed no significant consistent phase shift. Ipsilateral radial and ulnar diameters, measured at the wrist level, exhibited similar and synchronous vasomotion patterns, despite differences in the amplitude. For all subjects, contralateral measurements, performed at two symmetrical sites of the radial arteries, showed similar oscillatory patterns with a strong correlation (0.85 < r < 0.99, n = 12). These results suggested the existence of a global regulatory mechanism that coordinates vasomotion in the large conduit arteries of the human arm.