The thermal properties of carbon nanofibers (CNF)/epoxy composites, composed of tetraglycidyl-4,4'-diaminodiphenylmethane (TGDDM) resin and 4,4'-diaminodiphenylsulfone (DDS) as a curing agent, were investigated with differential scanning calorimetry (DSC), thermogravimetric analysis, and dynamic mechanical thermal analysis. DSC results showed that the presence of CNF had no pronounced influence on the heat of the cure reaction. However, the incorporation of CNF slightly improved the thermal stability of the epoxy. Furthermore, the storage modulus of the TGDDM/DDS epoxy was significantly enhanced, whereas the glass-transition temperature was not significantly affected, upon the incorporation of CNFs. The storage modulus of 5 wt % CNF/epoxy composites at 25 degrees C was increased by 35% in comparison with that of the pure epoxy. (c) 2006 Wiley Periodicals, Inc.