Palladium (Pd) anode catalyst shows high electrocatalytic oxidation activity under ambient conditions for direct formic acid fuel cell (DFAFC) operation. However, the highly active Pd is susceptible to significant catalyst poisoning by impurities present in the fuel. In this study, the effect of methyl formate, methanol, and acetic acid impurities on DFAFC performance was investigated. These organic impurities will increase the poisoning rate of the highly active Pd catalyst, resulting in a reduction of fuel cell power output. The impact on performance of various levels of impurities is reported. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3080691] All rights reserved.