A metal implant for use in a surgical procedure is provided with a surface layer that is integral with the metal substrate, and which incorporates a biocidal material. The surface layer may be grown from the metal substrate, by anodising, and the biocidal material incorporated in it by ion exchange. Alternatively the layer may be deposited by electroplating, followed by diffusion bonding so as to become integral with the metal substrate. In either case, silver is a suitable biocidal material; and both the release rate and the quantity of biocidal material should be low to avoid toxic effects on body cells. Electropolishing the surface before formation of the surface layer is also beneficial, and this may be achieved by electropolishing.