Intra-arterial tolazoline has been used as an adjunct for angiographers and has been investigated for application in certain peripheral vascular disorders secondary to its potent activity as a vasodilator. We have had experience with three cases in which severe peripheral arterial trauma had resulted in nonviable extremities in spite of both orthopedic manipulation and vascular reconstruction. Continuous infusions of intra-arterial tolazoline were begun with marked improvement in blood flow in all extremities and resultant viability in all three within 48 hours. All three of these extremities, although severely traumatized, had one patent vessel distal to the popliteal trifurcation which was patent and which insured at least some flow to the distal extremity. Canine experiments were performed which demonstrated that intra-arterial tolazoline increased distal limb blood flow but did not moderate muscle surface hydrogen ion increase. These experiments confirm that the most important effect of the drug is in opening of precapillary arteriovenous shunts in the skin which increase total blood flow in medium and large size blood vessels in the injured limb. Major systemic effects of the drug were not observed when used in these specified concentrations and when monitored carefully by nursing personnel. We therefore feel that infusion of tolazoline can be used in specified cases of peripheral arterial trauma when both orthopedic and vascular reconstruction have not restored adequate blood flow to the traumatized extremity.