Abstract: Copolyesters of improved dyeability are formed from dicarboxylic acid components and glycol components. The new polyesters are characterized in that more than 80 mol percent of the dicarboxylic acids is terephthalic acid or its ester-forming derivative and that more than 80 mol percent of the glycols is a glycol or two or more glycols selected from ethylene glycol, tetramethylene glycol and 1,4-cyclohexane dimethanol and 1 to 10 weight percent thereof, based on the resulting polyester is a glycol represented by the following formula (I):HO--(C.sub.k H.sub.2k O).sub.m --R--O--(C.sub.l H.sub.21 O).sub.n --Hwherein R is a divalent aliphatic hydrocarbon group having 4 to 20 carbon atoms, K and l are same or different integers of 2 to 4, m and n are same or different integers, and 1.ltoreq.m+n.ltoreq.10.