Effects of electrical stimulation of mesencephalic pressor areas on peripheral hemodynamics were investigated in isolated hindlimbs of the dogs anesthetized with [alpha]-chloralose. Perfusion pressure and venous outflow were measured in the isolated hindlimbs perfused at constant flow. Perfusion pressure gave triphasic changes by the stimulation. The 1st phase is caused by vasoconstriction via vasoconstrictor nerves. The 2nd phase corresponds with vasodilatation via cholinergic vasodilator nerves. The 3rd phase is delayed vasoconstriction mediated by humoral pressor substances. Increase in venous outflow, independent of perfusion pressure, indicates venoconstriction by the stimulation.