A novel polymer-forming diimide-diacid, 2,6-bis(4-trimellitimidophenoxy)naphthalene, was prepared by the condensation reaction of 2,6-bis(4-aminophenoxy)naphthalene with trimellitic anhydride (TMA). A series of novel aromatic poly(amide-imide)s containing 2,6-bis (phenoxy)naphthalene units were prepared by the direct polycondensation of the diimide-diacid with various aromatic diamines using triphenyl phosphite (TPP) in N-methyl-2-pyrrolidone (NMP)/pyridine solution containing dissolved calcium chloride. Thirteen of the obtained polymers had inherent viscosities above 1.01 dL/g and up to 2.30 dL/g. Most of polymers were soluble in polar solvents such as DMAc and could be cast from their DMAc solutions into transparent, flexible, and tough films. These films had tensile strengths of 79-117 MPa, elongation-at-break of 7-61%, and initial moduli of 2.2-3.0 GPa. The wide-angle X-ray diffraction revealed that some polymers are partially crystalline. The glass transition temperatures of some polymers could be determined with the help of differential scanning calorimetry (DSC) traces, which were recorded in the range 232-300 degrees C. All the poly(amide-imide)s exhibited no appreciable decomposition below 450 degrees C, and their 10% weight loss temperatures were recorded in the range 511-577 degrees C in nitrogen and 497-601 degrees C in air.