Ternary Fe-Mo-R (R = Rare Earth metal) crystalline alloys, Fe(75)Mo(20)Gd(5), Fe(75)Mo(20)DY(5), Fe(75)Mo(20)Er(5) and Fe(75)Mo(20)MM(5) (MM = mischmetal: 50.2% Ce, 26.3% La, 17.5% Nd, 6.0% Pr, atomic %) have been characterized by means of microstructural and electrochemical techniques in view of their possible applications as electrocatalytic materials for hydrogen evolution reaction (HER). The microstructure of the alloys was examined by scanning electron microscopy coupled with electron probe microanalysis; XRD measurements were also performed. The electrochemical efficiency of the electrodes has been studied on the basis of electrochemical data obtained from steady-state polarization and electrochemical impedance spectroscopy (EIS) techniques in 1 M NaOH solution at 298 K. The results were compared with those obtained on a binary Fe-Mo commercial alloy (Fe(80)Mo(20), atomic %). Moreover, literature data concerning the electrocatalytic activity of the Ni(75)Mo(25) and Co(75)Mo(25) crystalline alloys, which are considered good electrocatalyst materials for the HER, were also reported for comparison. The microstructural features play a fundamental role in determining the electrocatalytic activity of the investigated alloys. The overall experimental data indicate that interesting electrocatalytic performances are displayed by the Fe(75)Mo(20)MM(5) electrode, which exhibits the highest activity towards the HER. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.