This study aimed at using scanning electron microscopy to study the Izod impact fracture surface morphology of super-tough nylon 6 blends prepared by blending nylon 6 with a maleic anhydride-grafted polyethylene-octene elastomer (POE) in the presence of a multifunctional epoxy resin (CE-96) as compatibilizer. The fracture surface morphology and the impact strength of the nylon 6 blends were well correlated. The fracture surface morphology could be divided into a slow-crack-growth region and a fast-crack-growth region. Under low magnification, the fractured surface morphologies of the low-impact-strength nylon 6 blends appeared to be featureless. The area of the slow-crack-growth region was small. There were numerous featherlike geometric figures in the fast crack growth region. The fractured surface morphologies of the high-impact-strength nylon 6 blends exhibited a much larger area in the slow-crack-growth region and parabola markings in the fast-growth region. Under high magnification, some rubber particles of the low-impact-strength nylon 6 blends showed limited cavitation in the slow-crack-growth region and featherlike markings in the fast-crack-growth region. Rubber particles of high-impact-strength nylon 6 blends experienced intensive cavitation in the slow-crack-growth region and both cavitation and matrix shear yielding in the fast-crack-growth region, allowing the blends to dissipate a significant amount of impact energy. A nylon 6 blend containing 30 wt % POEgMA exhibited shear yielding and a great amount of plastic flow of the matrix throughout the entire slow-crack-growth region, thus showing the highest impact strength. (C) 2000 John Wiley & Sons, Inc.