A series of wholly aromatic thermotropic copolyesters based on 4-hydroxybenzoic acid, hydroquinone, and 2,6-naphthalene dicarboxylic acid were synthesized by direct melt polymerization with or without different added transesterification catalysts. Nine procedures for calculation of the intrinsic viscosities from a single viscosity measurement for polymer solutions, including a proposed one, were applied for the thermotropic copolyesters in 1,1,1,3,3,3-hexafluoro-2-propanol at 30 degreesC. Various forms of the Huggins and Kraemer equations, singly or combined, yielded intrinsic viscosities that were in good agreement with extrapolated values obtained in the usual manner from multipoint viscosity measurements over a wide range of concentrations.