Direct esterification of a hydroxyl functional polyester resin with p-hydroxybenzoic acid (PHBA) was carried out at 200-230 °C in the presence of p-toluene sulphonic acid and xylene. Acid value, molecular weight distribution, differential scanning calorimetry and both 1H and 13C NMR analysis were used to monitor the reaction. The optical texture of the final products were examined using a polarizing optical microscope. The products from the reaction were the polyester with approximately 1 PHBA molecule per polymer chain end and unreacted PHBA. The dominant reaction in the system appears to be transesterification, resulting in a decrease of the molecular weight during the reaction. A liquid crystalline phase was not formed as multiple grafts of PHBA were not formed.