Observations are reported on carbon black-filled thermoplastic elastomer (TPE) in uniaxial loading-unloading tensile tests with various strain rates (ranging from 7 x 10(-4) to 1 x 10(-1) s(-1)) at temperatures in the interval from 25 to 90 degrees C. A constitutive model is derived for the viscoplastic response of a TPE composite at three-dimensional deformations with finite strains. The stress-strain relations involve six adjustable parameters that are found by fitting the experimental data. It is shown that the model correctly describes the observations, and its parameters are affected by temperature and strain rate in a physically plausible way. (C) 2009 Elsevier Ltd. All rights reserved.