Abstract: An endoprosthesis comprised of a resorbable outer shell or coating material housing a filling material provides practical and cosmetic advantages. The outer shell or coating is resorbed back into the body within 12 months of implantation. Materials such as polyurethane, at an appropriate thickness, serve as an outer shell and provide the endoprosthesis with a shape as well as rendering the endoprosthesis implantable and easily handled by the surgeon. Once implanted, the outer shell or coated is resorbed into the body. The filling material, on the other hand, is biostable and biocompatible. The filling material is in the form of a hydrogel with a viscosity suited for the purpose. Polyacrylamide is a well suited hydrogel since it is biocompatible and can be formulated to the appropriate viscosity. The endoprosthesis of the invention can be used for soft-tissue replenishment such as in the face and breasts, or in the joints for support, or in an internal conduit to provide bulking.