Abstract: Tetrahydrophthalic anhydride for the preparation of polyesters is conveniently prepared in a stable, liquid form for transportation and storage by adding molten anhydride to a 100.degree. to 120.degree. C., C.sub.2 to C.sub.9 glycol at rate to maintain this temperature range without raising the temperature of the mixture in increments of more than 5.degree. F., reacting the mixture for a sufficient time to reduce the acid number of the mixture to a number in the range below the theoretical acid number for the half ester of the glycol and anhydride and 165; thereafter cooling the mixture to 155.degree. C., adding glycol as necessary to provide a mole ratio of glycol to anhydride in the range of 1.2 to 2:1 and cooling the mixture to a temperature in the range of 40.degree. to 70.degree. C.