Effect of carbon addition on activation and hydrogen sorption characteristics of TiMn1.25Cr0.25 alloy is investigated. With increasing carbon contents, the lattice constants and the unit cell volume decrease. The activation of TiMn1.25Cr0.25 alloy becomes easier with the increasing carbon content. Auger electron spectroscopy (AES) results show that carbon addition does not reduce the thickness of oxide layer formed on the surface of TiMn1.25Cr0.25 alloy, but makes the Ti/Mn ratio of alloy top surface become closer to the bulk components, which probably is one of the reasons for the improvement of alloy activation performance. Pressure-composition-temperature (PCT) results present that carbon addition decreases hydrogen absorption capacity and increases the hydrogen absorption-desorption plateau pressure. In addition, the cycle-life of hydrogen absorption-desorption increases with increasing carbon concentration. (C) 2003 Elsevier B.V. All rights reserved.