Abstract New phosphorus-containing homo- and copolyesters were prepared from 2,8-dihydroxy-5phenyl-5H-dibenzophosphole 5-oxide, bisphenol A and diacid chlorides, and their solubility, thermal stability, flame resistance and photochemical stability were investigated. Most of the polyesters were obtained at relatively low viscosities. Incorporation of the dibenzophosphole ring into the polymer backbone was found to improve solubility in polar aprotic solvents, flame resistance, and stability to u.v. light. The dibenzophosphole-containing homo- and copolyesters had initial decomposition temperatures comparable to those of phosphorus-free polyarylates.