The remarkable stability of ruthenium Prussian blue analogue (designated as RuOx-PB) in strongly acidic media and for the enzymeless electrocatalytic oxidation of glucose was demonstrated in this study. The RuOx-PB combinative film neither dissolves nor denatures in concentrated acids, such as HClO4, HCl, H2SO4, and HNO3, investigated in this study. The catalytic response was found to directly proportional to [H+]. Such features are unique since neither RuOx- nor PB-based compounds are effective for direct carbohydrate oxidation in acidic media. The RuOx-PB film showed a highly reversible redox peak at similar to 1.2 V in 5 M HClO4 as a result of the fast proton-coupled electron transfer behavior of high valent ruthenium intermediate, Ru-VII/VI. The formation of internal multiple-hydrogen bond as well as the generation of the > Ru-VII=O species in strongly acidic media were proposed to play a key role in this feature. The RuOx-PB holds high potential for use in catalytic oxidation, corrosion protection, biofuel cell, etc. (c) 2006 Elsevier B.V All rights reserved.