A nickel catalyst to be used for internal steam reforming in a molten carbonate fuel cell (MCFC) must be resistant to the alkali components (Li and K species) of the electrolyte; these components can reach the catalyst from the anode by either transport via the vapor phase or by means of surface creep along the walls. In a series of experiments for determining the rates of transport, it was found that the amount of alkali transported by creep along a metallic wall (Au or Ni) was much smaller than that transported via the vapor phase. The vapor transport occurred by the formation of the alkali hydroxides. The vapor pressure of LiOH was found to be eight times larger than that calculated from thermodynamic data. All the Al-containing materials tested strongly took up alkali from the gas phase. The catalysts Ni/MgO and Ni/SiO2 sintered strongly during exposure to gaseous LiOH and KOH.