Abstract: A gasket for a rotary gate valve is made from a material that can be utilized only after sintering, such as a fluorocarbon polymer, and comprises a ring-shaped solid portion 15 surrounded by a coaxial, annular flange 16 for anchoring the gasket within the valve body. A closed chamber 23 is provided in the solid portion of the gasket and houses an elastic ring 28. In manufacturing the gasket an annular ring is formed comprising the solid portion 15, an axial groove 23, an axial tab 29, and a radial tab 30. The elastic ring 28 is then inserted in the axial groove, and the tabs 29 and 30 are pressed together to form the annular flange 16 and fully enclose the ring 28.