We report a high-shear processing technology that allows the homogenous dispersion of unmodified multiwalled carbon nanotubes (UMWNTs) in a thermoplastic elastomer, poly(styrene-b-butadiene-co-butylene-b-styrene) (SBBS). We demonstrated that the dispersion of UMWNTs in a polymer matrix depends greatly on the shear stress exerted during melt processing. Mechanical tests showed that the tensile modulus, tensile strength and elasticity of the composites with fine nanotube dispersion processed at a high-shear rate are much higher than those of the composites processed at a low shear rate. The results indicated that high-shear processing is an effective method of improving the dispersion of unmodified carbon nanotubes in a polymer matrix. (c) 2007 Elsevier Ltd. All rights reserved.