Novel copolymers and terpolymers of the amide-imide type are prepared from tricarboxylic acid anhydride compounds, N,N'-diacylated diamines, N-acylated diamines, and primary diamines. These copolymers and terpolymers are useful for preparing injection molded articles of superior properties. A novel process for the manufacture of amide-imide copolymers and terpolymers is disclosed wherein the imide, imide-imide, amide, and amide-amide moieties incorporated into the polymer backbone can be controlled by acylating the amine functionality which is to form the amide and amide-amide moieties while reacting directly those diamines with a tricarboxylic anhydride compound which are intended to form the imide and imide-imide moieties.