Ni-S-Co alloy was obtained through electrodeposition in a modified Watts bath by adding thiourea (TU) and CoCl2 into the bath. The structure and morphology were determined by XRD and SEM respectively. The contents of S and Co were measured by EPMA correspondingly. The electrochemical properties, including the hydrogen evolution overvoltages eta (h.o.v.), the Tafel slope b and the exchange current density i(o) of amorphous Ni-S-Co cathode were measured. The HER mechanism and the steady-state behavior of amorphous Ni-S-Co alloy in alkaline media were also investigated. The results indicate that the structure of Ni-S-Co alloy obtained is amorphous and it shows much higher electrochemical activity than other electrodes including amorphous Ni-S and Ni-S(La) electrodes partially due to the higher sulfur content in such electrode. The HER mechanism is a fast Volmer reaction following a slow Heyrovsky reaction and the high electrocatalytic HER property is mainly due to the large amount of adsorbed H atoms. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.