Electrocatalysts containing iridium and platinum‐iridium alloys have shown very encouraging levels of performance when used as anodes in ammonia fuel cells. These materials were appreciably more active than platinum alone, and the open‐circuit voltage and polarization under load generally improved with increasing iridium content. Data are presented for ammonia/oxygen cells at 100°–120°C using 54% potassium hydroxide as electrolyte and platinum ‐iridium blacks and Pt/Ir supported on boron carbide and graphite as anodes. The observed electrochemical activity of iridium appears to be related to the unique activity of this metal in the gas phase catalytic decomposition of ammonia. Supported iridium catalysts were also found to be effective in an external cracking unit maintained at 350°–450°C and coupled to a hydrogen fuel cell system. In this case enhanced performance was observed when small amounts of oxygen were introduced with the ammonia into the catalytic reactor.