The deformation behaviour of polyoxymethylene has been studied in plane strain compression at temperatures from 120 degrees C up to 165 degrees C and in uniaxial tension and simple shear at 160 degrees C for strain rates from 10(-4) to 1 s(-1). In uniaxial tension the stress-strain behaviour was determined by a novel video-controlled testing system. The measurements showed that there was a very significant evolution of volumetric strain, indicating that damage mechanisms play a key role in the plastic deformation behaviour. All tests showed similar deformation stages with a short region of visco-elastic behaviour followed by a rounded yield point. The von Mises equivalent yield stress for these tests showed a linear relationship with logarithmic strain rate, suggestive of an Eyring type thermally activated process. After yielding, all stress-strain curves showed a long plastic deformation regime, which in shear occurred at constant stress. In plane strain compression there was also only a very small increase in stress, in contrast to uniaxial tension where very significant strain hardening was observed at high strains, which is attributed to the onset of structural changes. (c) 2006 Elsevier Ltd. All rights reserved.