The effect on distal blood flow in a 2 vessel limb of clamping one of the vessels or resecting it over a length is not known. Commonly this situation occurs clinically, for example, following lacerations to the radial or ulnar artery or as a result of removing a radial or ulnar artery flap. In a dog model established to mimic these clinical circumstances, a 2 vessel limb was created in which one vessel carried two-thirds of the total flow and the other one-third. Electromagnetic flow recordings were taken to measure the changes in flow in one vessel when the other was clamped or resected. Contrary to expectation, when one vessel was occluded the flow in the opposite vessel both immediately and for the following 30 minutes increased but remained well below the combined flow of 2 unclamped vessels. No increased flow was recorded in the dominant vessel when the smaller vessel was clamped, while an approximately 25% increase in flow was recorded in the smaller vessel when the larger one was clamped. This represents a reduction in total distal blood flow of one-half of the preclamping levels. Clamping of the vessel or its resection over a length resulted in the same degree of alteration in flow in the opposite vessel. The sacrifice of a dominant vessel in a 2 vessel limb whether by simple ligation or by radical stripping as for free tissue transfer significantly decreases distal flow in that limb at least in the immediate and short term.(ABSTRACT TRUNCATED AT 250 WORDS)