The hydrogen evolution reaction (HER) of nanocrystalline Ni-Mo-B alloys was investigated in alkaline solution in comparison with the corresponding crystalline materials and polycrystalline nickel. The nanocrystalline alloys, prepared by melt spinning, were investigated towards the HER in 1 M KOH solution at 298 K. An electrochemical activation procedure (cyclic reduction-oxidation pre-treatment) was used to enhance the apparent HER activity. In case of the crystalline Ni-Mo-B master alloys the origin of the activity can mainly be attributed to an increase of the real surface area (roughening) caused by a dissolution of Mo-containing phases. Interestingly, a roughening of nanocrystalline Ni-Mo-B alloys did not occur, probably, because of the very homogenous and fine microstructure of these materials. The higher HER activity of the nanocrystalline Ni-Mo-B alloys is obviously caused by a higher intrinsic activity of the nanocrystalline Ni-Mo-B alloys and a synergistic effect of Mo. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.