Oxygen reduction catalysts were prepared by heat treatment of carbon supported iron phenantroline complexes in Ar or NH3. The optimum carbon black loading with iron was found to be 2%, the optimum heat treatment temperature was about 800 degreesC. X-ray diffractogramms and TEM showed the occurrence of crystalline species at higher catalyst loadings; however, these species seem not to contribute significantly to the catalytic activity. From the slope of the Koutecky-Levich plot, an average number of 3.7 electrons transferred per oxygen molecule was calculated, which is consistent with RRDE data. A Tafel slope of about 120 mV (decade)(-1) indicates that the first electron transfer is rate determining.