New poly(amide-imide)s were prepared from a diimide-dicarboxylic acid, 1,4-bis(4-trimellitimidophenoxy)-2-tert-butylbenzene (BTTB), with various diamines by the direct polycondensation in N-methyl-2-pyrrolidinone (NMP) using triphenyl phosphite and pyridine as condensing agents. The new diimide-dicarboxylic acid BTTB containing an ether linkage and tert-butyl substituent was synthesized by the condensation reaction of 1,4-bis(4-aminophenoxy)-2-tert-butylbenzene with trimellitic anhydride. All the polymers were obtained in quantitative yields with inherent viscosities of 0.62-1.06 dL g Ϫ1 . The polymers were amorphous, and most of them were readily soluble in aprotic polar solvents such as NMP, N,N-dimethylacetamide (DMAc), and N,N-dimethylformamide (DMF), as well as in less polar solvents such as dimethyl sulfoxide (DMSO), m-cresol, pyridine, and ␥-butyrolactone, and also even in tetrahydrofuran. The glass transition temperatures of the polymers were determined by DSC method, and they were in the range of 238 -279°C. These polymers were stable up to 408 -449°C in air and 451-483°C in nitrogen and lose 10% weight in the range of 479 -525°C in air and 480 -528°C in nitrogen atmosphere. The polymer films had a tensile strength range of 71-115 MPa, an elongation at break range of 4 -14%, and a tensile modulus range of 2.3-3.1 GPa.