Polyphenylene sulfide is a new engineering plastic characterized by a unique combination of useful environmental, mechanical, and flame resistant properties. This paper presents a variety of new developments in molding methods and long term properties of polyphenylene sulfide. Optimum conditions for fabrication by injection molding, compression molding, and free sintering techniques are described along with a comprehensive tabulation of mechanical, factional, and electrical properties of various filled and unfilled compositions. The effect of injection molding conditions and post-treatments, such as annealing, on mechanical behavior is discussed. Long term stability of molded specimens of the polymer to a variety of chemical environments as well as oven aging studies are reported. The significance of these properties is illustrated by a discussion emphasizing new applications for various compositions based on polyphenylene sulfide.