A series of new aromatic poly(amide-imide)s were synthesized by the triphenyl phosphite activated polycondensation of the diimide-diacid, 1,4-bis(trimellitimido)-2,5-dimethylbenzene (I), with various aromatic diamines. The poly(amide-imide)s had inherent Viscosities of 1.13-2.22 dL/g. Most of the resulting polymers showed an amorphous nature and were readily soluble in a variety of organic solvents. Transparent, flexible, and tough films of these polymers could be cast from DMAc or NMP solutions. Their cast films had tensile strengths ranging from 64 to 116 MPa, elongations at break from 6 to 20%, and initial moduli from 2.18 to 3.90 GPa. The glass transition temperatures of these polymers were in the range of 247-324 degrees C.