Venous occlusion plethysmography was used to measure the effect of changes in limb position on the peripheral blood flow. The validity of the method with the limb dependent was investigated, and found to be reliable in the conditions of the experiment. The blood flow in the limb was found to be decreased when it was raised or lowered 45 degrees. At 15 degrees of elevation, the flow was increased. Similar changes were found in recently sympathectomized limbs. The reactions may therefore be regarded as local vascular responses to postural change.