The need for new improved structural resins which meet the requirements of advanced aircraft, space, and deep submergence vehicles has served as the impetus for research in this area. During the last 10 years, a significant amount of effort has concentrated on new thermally stable organic and heterocyclic polymers. The polyquinoxalines (PQ) have evolved from this effort and represent one of the most promising heterocyclic polymer systems currently known for potential use in structural application which demand high thermal, oxidative, and hydrolytic stability. The following discussion will be confined to the linear nonladder-type PQ.