Dispersant-free PTT dyeing of temporarily solubilized azo disperse dyes based on pyridone moiety which contain $eta$-sulfatoethylsulfonyl group was investigated. The dyes were successfully applied to PTT without the use of dispersants. The color yields of the dyes on PTT fabric were dependent on dyeing pH as well as dyeing temperature. The optimum results were obtained at pH 5-6 and $110^{circ}C$. The dyes showed alkali-clearing property and exhibited good to excellent fastness on the PTT fabric. The COD levels of the dyeing effluent from the temporarily solubilized disperse dyes were much smaller than those from commercial disperse dye.