Effects of a maleated triblock copolymer of styrene-(ethylene-co-butene)-styrene (SEBS-g-MA) on compatibilization and mechanical properties of nylon-12,12/nylon-6 blends were investigated. The results showed that addition of SEBS-g-MA could improve the compatibility between nylon-12,12 and nylon-6. Nylon-12,12 could disperse very well in nylon-6 matrix, although the dispersion of nylon-6 was poor when nylon-6 was the dispersed phase. At a fixed nylon- 12,12 / nylon-6 ratio of 30/70, supertoughness was achieved with addition of 15% SEBS-g-MA in weight. Scanning electron microscopy of the impact-fractured surface indicated that cavitation and matrix shear yielding were the predominant mechanisms of impact energy dissipation. (C) 2004 Wiley Periodicals, Inc.