A device for promoting endothelial cell motility and / or vascularisation in man and other vertebrate animals which comprises a carrier such as a sheet or tube of a plastic material, which carrier is impregnated or coated with a source of copper I, copper II or tin II ions such that when applied to or inserted into an animal the ions can diffuse into the surrounding tissue of the animal. The device can be used to promote vascularisation after surgery or on parts of the body lacking adequate vascularisation such as skin ulcers. It can be used in the form of a tube for arterial by-pass surgery wherein the increased motility of the endothelial cells causes faster carbonisation of the interior of the tube and thereby lessens the risk of blood clots forming during such surgical procedures.