The temperature-dependent relative contributions of slip, twinning, and slip-twin interactions to the deformation response of a high-manganese austenitic steel were investigated under impact loading. Thorough transmission electron microscopy and scanning electron microscopy showed that either twinning or slip dictates the deformation response under impact loading, as opposed to the slip-twin interactions typically observed in high-manganese austenitic steels under tensile or compressive loading. Specifically, slip dominates at elevated temperatures, whereas slip activity is restricted by enhanced twinning at low temperatures, and the parameters, such as twin volume fraction, twin thickness and length, or glide dislocation density, show a strong temperature-dependence. The enhanced activity of only one mechanism rather than the slip-twin interaction is associated with the high-strain rate deformation taking place under impact loading, which does not allow for significant interaction of the two mechanisms. (C) 2013 Elsevier B.V. All rights reserved.