Two series of new, wholly aromatic copolyesters were prepared from 6-hydroxy-5-phenyl-2-naphthoic acid (HPNA) or 4’-hydroxy-3’-phenyl-biphenyl-4-carboxylic acid (HPBA) and 4-hydroxybenzoic acid (HBA) in varying mole ratios. In addition to these copolyesters, the homopolyesters of B-hydroxy 5-phenyl-2-naphthoic acid and 4’-hydroxy-3’-phenylbiphenyl-4-carboxyli acid were synthesized. These polyesters were characterized by differential scanning calorimetry, wide angle X-ray diffractometry, thermogravimetry, and polarized microscopy for the study of their thermal transitions, crystallinity, thermal stability, and mesophases. In general, the HPNA copolyesters revealed greater degrees of crystallinity and higher melting temperatures than the HPBA copolyesters. This difference is attributed to the planar naphthalene moiety in the HPNA structure. In contrast, the two phenylene rings of the HPBA unit along the backbone are conjectured not to be coplanar. All of the polyesters formed liquid crystalline mesophases above their melting temperatures.