Polyamides and polyimides having 4,4"-o-terphenyldiyl units in the main chain were synthesized. The polyamides were prepared from 4,4"-diamino-o-terphenyl and aromatic dicarboxylic acids or aromatic dicarbonyl dichlorides. The polyimides were prepared from 4,4"-diamino-o-terphenyl and aromatic tetracarboxylic dianhydrides. Copolyamides and copolyimides were also prepared using 4,4"-diamino-o-terphenyl and other diamines. The T-g values of the polyamides were high (283-298 degrees C). The polyamides were soluble in cyclohexanone and pyridine. The polyimides also possessed high T-g values (298-372 degrees C). The solubilities of the polyimides, on the other hand, were poor. The introduction of o-terphenyl units into the main chain of the polyamides led to high thermal stability as well as good solubility.