Poly(vinyl chloride) (PVC) is a commodity plastic that is frequently used in geosynthetic applications. Its performance is important to the safety of landfills, where potentially dangerous chemicals must be segregated from the outside environment, such as groundwater, for considerable lengths of time. This review paper describes PVC and the modes of degradation that can affect its properties when it is used as a geosynthetic. These modes of degradation must be addressed by the PVC producers, the manufacturers of the geosynthetics, and the landfill operators.