Hydrogen absorption pressure-composition (PC) isotherms and kinetics of rhombohedral MmTM(3) (TM = Ni, Fe and Co) alloys have been carried out using Sieverts type apparatus. The variations in plateau pressure, hydride stability and kinetics upon partial substitution of Fe or Co for Ni in MmNi(3) have been discussed. The absorption kinetics have been analyzed based on the Johnson-Mehl-Avrami (JMA) model. The reaction order and rate constants have been determined from the fit of the JMA model to the experimental data. The existence of different hydride phases and the hydriding reaction process in the different phase regions have been identified and explained. Further, the temperature dependent electrical resistivity of alloys and their hydrides have been studied and the variations in the resistivity with hydrogen concentration have been discussed. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.