Neurally induced venoconstriction has been investigated in a dog's limb with arrested circulation and muscle paralysis at various degrees of venous distension. The increment of venous pressure on stimulation of the lumbar sympathetic was less when the initial venous pressure was high than when it was low. Similar relationships were observed when venoconstriction was reflexly elicited by sudden inflation of the lungs, and in an isolated venous segment on lumbar sympathetic stimulation.