A series of new aromatic poly(amide-imide)s were synthesized by the triphenyl phosphite-activated polycondensation of the diimide-diacid, 2,5-bis(trimellitimido)chlorobenzene (Iota) with various aromatic diamines in a medium consisting of N-methyl-2-pyrrolidone (NMP), pyridine, and calcium chloride. The poly(amide-imide)s had inherent viscosities of 0.76-1.42 dL g-l. The diimide-diacid monomer (I) was prepared from 2-chloro-p-phenylenediamine with trimellitic anhydride. Most of the resulting polymers showed an amorphous nature and were readily soluble in a variety of organic solvents, including NMP and N,N-dimethylacetamide. Transparent, flexible, and tough films of these polymers could be cast from N,N-dimethylacetamide or NMP solutions. Their cast films had tensile strengths ranging from 74 to 95 MPa, elongations at break from 7 to 11%, and initial moduli from 1.38 to 3.25 GPa. The glass transition temperatures of these polymers were in the range of 233 degrees-260 degrees C, and the 10% weight loss temperatures were above 450 degrees C in nitrogen.