Abstract: Disclosed is a method for forming a gasket seal or transition fitting affixed to one of two parts to be joined in a gasketed joint by use of the gasket. The method includes the step of providing a mold having a walled mold cavity of the shape desired for the gasket, at least one wall of the mold cavity being a junction surface of the one part and the remaining walls of the mold cavity being formed in a mold piece. The mold is closed by placing the mold piece over the junction surface of the one part to establish the mold cavity as a closed generally toroidal volume. Then a molten gasket-forming thermoplastic material is injected into the mold cavity to form the gasket, the thermoplastic material including a bonding agent for establishing an adhesive bond between the junction surface and the gasket. The thermoplastic material is cooled to solidify the gasket and affix it to the junction surface and the mold piece is removed away from the junction surface.