L-Ascorbic acid (vitamin C), which is an environmentally and biologically friendly compound, was applied as a fuel for direct polymer electrolyte fuel cells. The main anodic reaction was the two-electron oxidation of L-ascorbic acid to dehydroascorbic acid, the same as its metabolic conversion. Various precious metals, such as platinum, palladium, iridium, ruthenium, and rhodium, were available as an anode catalyst for the electro-oxidation of L-ascorbic acid. Moreover, the direct L-ascorbic acid fuel cell could be operated even without an anode catalyst. (C) 2003 The Electrochemical Society.