Abstract: A leak-proof implantable breast prosthesis and a method for making the prosthesis. The breast prosthesis comprises an elastically deformable body or core which is encased within a flexible biocompatible elastomeric shell. In one embodiment, the deformable body is attached, in segments, to the inner surface of the shell by adhesive means and has shape-memory. In another embodiment, the shell encases the core but is not attached to the core. When the outer shell of the prosthesis is subjected to a deforming force, the prosthesis deforms then returns to an original shape when the deforming force is removed. In the event that the shell is ruptured, the prosthesis cannot leak exogenous filler fluid into the surrounding tissue because the prosthesis is substantially void of exogenous filler fluid.