Preferable aromatic polyesters are those having substituents at the 3 and 5 positions of the dihydric phenol component, wherein a part or all, especially at least 5% by mole, of the recurring units (I) are units of the formula (II): ##STR2## wherein X, m and n are as defined above, and R1, R2, R3 and R4 are a monovalent group selected from the group consisting of an alkyl group having 1 to 4 carbo