A series of copolyesterimides was prepared from bisphenol A, diacid (terephthalic acid [TPA] or isophthalic acid [IPA]), and 4-carboxy-N-(p or m-hydroxyphenyl)phthalimide (M1 or M2) in the presence of diphenyl chlorophosphate (DPCP) and pyridine as the direct condensation agent. Copolyesterimides derived from M1 showed poorer solubility than that of M2 during polymerization; a lower M1 content should be employed to prevent precipitation of the resulting polymers. The inherent viscosities of copolyesterimides were in the range of 0.33-0.56 dL/g. Some of these copolyesterimides were completely soluble in N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAC), dimethylformamide (DMF), and m-cresol. The thermal properties of copolyesterimides were examined by DSC and TGA. These copolyesterimides had glass transition temperatures in the range of 173-220-degrees-C and a 5% weight loss was observed in the range of 435-482-degrees-C.