Canine lateral saphenous vein and human greater saphenous vein were studied together to determine similarities and differences. Helical strips of both vessels contracted to norepinephrine with similar sensitivity. Canine veins developed more isometric tension than human veins treated similarly. Histological studies show canine veins to have little connective tissue and a single circular layer of smooth muscle. Human veins have much connective tissue and three layers of smooth muscle, an inner circular layer, middle longitudinal layer and outer circular layer.