Abstract: An aromatic polyester copolymer consisting of 10 to 90 mol % of a recurring unit of the formula: ##STR1## and 90 to 10 mol % of a recurring unit of the formula: ##STR2## and having a logarithmic viscosity number of at least 0.3 as measured in a mixture of phenol and tetrachloroethane (6:4 in weight ratio) at a concentration of 1 g/100 cc at 25.degree. C. and having a terminal carboxyl content of about 80 mol eq./ton or less. This aromatic polyester copolymer has high durability under dry and moist heat as well as high resistance to water crazing and hence can be fabricated into useful articles by various molding techniques.