A copolyester blend resistant to ultraviolet radiation consists essentially of a polyethylene terephthalate based copolyester having 1,4-cyclohexanedimethanol residues; an effective amount of an ultraviolet radiation absorber selected from the group consisting of benzoxazinones, dimeric benzotriazoles, triazines and mixtures thereof; and from about 2 to about 25 mole percent of 4,4'-biphenyldicarboxylic acid residues present in the copolyester wherein the mole percent is based on 100 mole percent of dicarboxylic acid or equivalents. The copolyester blend is useful in making UV radiation resistant thermoformed articles.