Abstract: Breast prostheses for subcutaneous implantation for breast augmentation. The prostheses include an outer shell having a smooth non-porous outer envelope and a non-woven porous outer layer affixed to the envelope. The outer layer is preferably manufactured by an electrostatic spinning process to deposit biocompatible polymeric fibers on the smooth outer envelope of the prosthesis to build up a porous surface which promotes tissue ingrowth therein. In a preferred embodiment, the biocompatible porous outer layer and the non-porous outer envelope are manufactured with a polyurethane polymer material. Most preferably, a polycarbonate urethane polymer is used to manufacture the outer layer. The outer envelope and the porous outer layer may be further treated with an acetoxy-terminated siloxane to render them more crack-resistant under in vivo use.