Aortic and vena caval pressures, right and left iliac flows. and pedal small artery and small vein pressures were recorded in mongrel dogs prior to and for 90 min following ligation of the right iliac, femoral, medical saphenous, and lateral saphenous veins. Total, arterial, small vessel and venous resistances were calculated. Measurements were repeated following alpha-receptor blockade (phenoxybenzamine) and perfusion of the extremities with a calcium chelator (EGTA). Results indicated that venous ligation resulted in constriction of small vessels in both the occluded and contralateral extremities and constriction of veins in the occluded extremity only. Relative responses of right and left vascular bed to alpha-blockade and EGTA perfusion suggested that small vessels were constricted bilaterally by enhanced sympathetic stimulation and that veins and small vessels were constricted on the occluded side in response to a local myogenic stimulus.