This review paper, which is based on bibliography data, is concerned with synthesis, properties and applications of polyimides with particular attention to the aromatic polyimides which are available in a variety of commercial forms and have become the standard of reference for performance of other high-temperature polymer materials. Syntheses of aromatic diamine-based polyimides cover the following polymers: polyamic acids and their conversion into polyimides, polyamideimides, and polyesterimides. Properties discussed include: thermal stability (structure vs. thermal stability, activation energy for thermal degradation); hydrolytic stability; radiation resistance; solution properties and mol. wt; UV stability; crystallinity; color; and transition temperatures. Properties of polyimide films and glass reinforced polyimide composites are tabulated. Refs.