Hydrogen evolution reaction (HER) was studied on two types of amorphous Ni-P and one type of Ni-S electrode, all prepared by an electrodeposition. It was found that the activity of these electrodes depended considerably on the thickness of the electrode layer. Electrodes With thicker layers were more active than thinner ones. Also the absorption of both forms of hydrogen (i.e. underpotential absorbed hydrogen H-HO and overpotential absorbed hydrogen H-HO) depended considerably on the layer thickness. On the other hand, the relative amount of absorbed hydrogen related to the layer thickness did not depend on this thickness. It followed from the results that the main cause of the high activity for the HER was the internal stress in the layer. The stress originated during the electrodeposition of layers by codeposited hydrogen that absorbed in forming layers.