Fully aromatic themotropic polyesters are based on(A) from 30 to 60 mol % of 4-hydroxybenzoic acid,(B) from 20 to 35 mol % of a mixture of(B.sub.1) terephthalic acid and(B.sub.2) isophthalic acid, the molar ratio of B.sub.1 to B.sub.2 being from 1.04:1 to 19:1, and(C) from 20 to 35 mol % of a mixture of(C.sub.1) hydroquinone,(C.sub.2) 4,4'-dihydroxydiphenyl and(C.sub.3) from 0 to 5 mol % of a dihydroxy compound of the general formula I ##STR1## where R and R' are each C.sub.1 -C.sub.4 -alkyl, halogen or aryl, n is 1, 2 or 3 and m is 0 or 1, the molar ratio of C.sub.1 to C.sub.2 being from 0.1:1 to 2.67:1 and the molar ratio of B to C being from 0.9:1 to 1.1:1.