The method of liquid chromatography has given the mean molecular characteristics of solutions of poly-(4,4′-oxydiphenylene pyromellitamic acid in the MM interval 2×10⁴-2·25 × 10⁵. An analytical expression has been obtained relating the constants of the Mark-Kuhn-Houwinck equation to such macromolecular parameters as the length of the Kuhn statistical segment, the mass of the monomer unit and the length of its projection on the direction of the extended trans-chain.