We report experimental observations on the drastically enhanced toughness in the high-strength and high-modulus ultrahigh molecular weight polyethylene (UFMWPE) films due to the addition of 1 wt% multiwalled carbon nanotubes (MWCNTs). A combination of tensile and Raman spectroscopic measurements showed that the presence of MWCNTs in the composites can lead to a similar to150% increase in strain energy density in comparison with the pure UPMWPE film at similar draw ratios. This is accompanied with an increase of similar to140% in ductility and up to 25% in tensile strength. We attribute the above observations to the chain mobility enhancement in UHMWPE induced by the MWCNTs. (C) 2003 Elsevier Ltd. All rights reserved.