A new family of high performance, miscible polymer blends based on aromatic polybenzimidazoles and aromatic polyimides has been discovered. Preliminary evidence, obtained with commercially available, soluble poly­mers suggests that polymers of these generic types may be miscible over a wide range of compositions and structural variations. Blend miscibility 

was evidenced in the form of single Tg's and well-defined single tan 6 relaxations intermediate to those of the component polymers, the formation 

of clear films and, in one case, enhanced solvent resistance.