A theory proposed for understanding the alloying effect on the hydrogen; overpotential of alloys has been further confirmed in the present study of intermetallic compounds, TiAl, FeAl and NiAl containing various 3d transition elements. The trend of hydrogen overpotential changes with alloying elements in these compounds resembled the observation in Ti-, Fe- and Ni-based binary alloys. The variation in hydrogen overpotential was explained in terms of the direction for the charge transfer between atoms as is shown in the transition metal based binary alloys. In other words, the most negatively charged atom in the compound, as the result of charge transfer between the constituent atoms, is responsible mainly for the hydrogen overpotential change with alloying. This concept was also applicable to the hydrogen overpotential problem for transition metal based ternary alloys.