The influence of plastic strain on the hydrogen evolution reaction (HER) on polycrystalline nickel, in H2SO4 electrolyte at 293 K, is studied a cathodic potential range. Linear polarisation curves and electrochemical impedance spectra show that the HER is described by a mechanism of Volmer-Heyrovsky, which parameters do not depend on plastic strain. The plastic strain modifies the density and the distribution of dislocations. These evolutions are well understood and lead to changes in the number of hydrogen additional adsorption sites, and then to changes in the current density developed on pre-strained samples. From 0 to 2.4% of plastic strain, the current density increases to reach a maximum value at 2.4%. This current density increase is directly linked to the dislocation density increase. Over 2.4%, the distribution of dislocations is modified and the current density decreases but keeps higher than the current density on an unstrained sample. (c) 2006 Elsevier Ltd. All rights reserved.