A partially amputated rat hind limb model was used to evaluate the potency of 1 percent, 2 percent, and 20 percent Xylocaine, 0.3 percent papaverine, and normal saline in both the treatment and prevention of blood-induced arterial spasm. Direct application of blood to the femoral artery was shown to produce a 60 percent reduction in limb perfusion. The 0.3 percent papaverine and 20 percent Xylocaine solutions were statistically superior to normal saline and the lower Xylocaine concentrations in their ability to relieve the blood-induced vasospasm and prevent further spasm. Normal saline, 1 percent Xylocaine, and 2 percent Xylocaine showed no preventive effect against blood-induced spasm. These findings emphasize the importance of good hemostasis in microsurgery, and simplify the choice of an effective spasmolytic agent.