Regional cerebral blood flow measurements were made in normal right-handed subjects by the 133 xenon inhalation method at rest and during movement of either hand. Left hand movement evoked a prominent focal flow increase in the right hemisphere in the Rolandic region. During right hand movement, there was a smaller and not statistically significant increase in left hemisphere Rolandic region. This suggests that more effort is required of right-handed subjects to move the left hand than the right, or that motor organization differs for left and right hand movements. Of several flow indices tested, there was little difference among gray matter flow rate, the product of gray matter flow and relative weight, the mean regional flow, and the initial slope index, all reflecting the flow changes with nearly equal sensitivity. The gray matter weight and fractional flow did not change consistently during hand movement.