Copolyesters were synthesized from bis(hydroxyethyl) naphthalate/bis(hydroxymethylcyclohexane)naphthalate (BHEN/BHCN) with various compositions. Copolyesters having intrinsic viscosities of 0.58-0.65 dL g were obtained by melt polycondensation in the presence of metallic catalysts. The optimum condition for polyethylene-1,4-cyclohexanedimethylene naphthalate (PECN) copolyester manufacturing is the transesterification under a nitrogen atmosphere for 4 h at a temperature of 245 +/- 5 degrees C followed by polymerization under 2 mmHg for 50 min at a temperature of 290-320 degrees C. Most copolyesters have better thermal stability than has poly(ethylene naphthalate) (PEN) and the effect of the cyclohexane-dimethylene structure on the thermal and crystalline properties of the resulting copolyesters was investigated using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Glass transition temperatures of the copolyesters were in the range of 115.2-138.4 degrees C, and 10% weight losses in nitrogen were all above 453 degrees C. The solubility, crystallinity, and moisture absorption of the copolyesters were also investigated.