The blends of poly(ether sulfone) and poly(aryl ether ketone) containing 1,4-naphthalene were prepared by melt mixing in a Brabender-like apparatus. The specimens for measurements were made by compression molding under pressure and then were water-quenched at room temperature. The tensile strength, tensile modulus, elongation at break, thermal analysis, and scanning electron microscopy were each measured. The dependence of tensile strength, tensile modulus, and elongation at break on blend systems was obtained. The effects of composition and miscibility on the mechanical properties are discussed. (c) 2005 Wiley Periodicals, Inc.