In this article, epoxidized carbon nanotubes (CNTs) are used to modify current epoxy resins. The produced epoxy groups on the nanotube surface significantly enriched nanotube chemistry and made them soluble in the organic solvents. Atomic force microscopy characterization indicated that epoxidized nanotubes were well dispersed in the organic solvent and most of them were isolated. Fracture surface of modified epoxy resins suggested that fracture toughness of the modified resins was significantly improved, demonstrating fracture characteristic of typical ductile materials. Epoxidized CNTs-modified epoxy resins demonstrated a 50% increase in the Young's modulus, 32% improvement in the tensile strength with 1 wt % loading. This study provides an effective way to synthesize novel epoxy resins. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 3322-3326, 2009