Tantalum-based compounds prepared by reactive sputtering with heating were evaluated as novel non-platinum cathodes for polymer electrolyte fuel cells. Effects of species of target, TaC and TaN, and the oxygen partial pressure on catalytic activity for the oxygen reduction reaction (ORR) were investigated. We found that TaC target was more useful than TaN to prepare specimens with high ORR activity. In addition, the existence of an appropriate amount of 0,) was needed with the TaC target to obtain superior catalytic activity for the ORR. XRD and TOF-SIMS analysis suggested that crystalline structure of TaON (monoclinic) and carbon on the surface might affect the catalytic activity for the ORR.