Thermodynamics predict high electrical efficiency, when converting methane directly in a fuel cell. This is possible in high temperature fuel cells, such as the molten carbonate (MCFC) and the solid oxide fuel cells (SOFC), utilizing the heat from the electrochemical reaction for the steam reforming of methane. The heat balance is not a limiting factor. Internal reforming in a molten carbonate fuel cell involves the risk of alkali poisoning of the catalyst. The mechanism of alkali-poisoning is discussed. Laboratory tests on alkali containing catalysts are described and data from internal reforming in a MCFC-plant are presented. On basis of a simple model, an assessment is made of the required catalyst activity. Only a few percents of the original activity is needed for 95% conversion.