Six all-naphthylene polyesters were prepared by the condensation of 1,4-naphthalenedicarboxylic acid (NA) chloride with 1,4-, 1,5-, 1,6-, 2,3-, 2,6- and 2,7-naphthalenediol (ND) isomers and effects of the isomerism of NDs on structure and properties of the polyesters were investigated. The polymers-1,4, -1,5 and -2,6 with more or less linear ND link were insoluble and the others with bent ND link were soluble in the mixed solvent from phenol/p-chlorophenol/1,1,2,2-tetrachloroethane(TCE). The polymer-2,6 with the most linear ND link did not show a T-g and the highest decomposition initiation temperature(T-D) and T-g’s and T-D’s of the other polymers were only marginally dependent on their structures. The polymer-2,3 is believed to have a macrocyclic structure consisting of four to six monomer units and the polymer-1,6 is amorphous in its stable chain conformation, while all the other polymers are semicrystalline. The polymers-1,4 and -1,5 exhibited an irreversible crystal-to-crystal transition at 380 and 320 degrees C respectively, whereas the polymer-2,6 a reversible one at 240 degrees C. The polymer-2,7 exhibited an irreversible crystal-to-amorphous transition at 360 degrees C.