The electrode kinetics of ferrocenium/ferrocene ([Fe(Cp)(2)](+)/Fe(Cp)(2)) was investigated in some room-temperature ionic liquids based on bis(trifluoromethylsulfonyl)amide. The diffusion coefficients of Fe(Cp)(2) were inversely proportional to the viscosity of the ionic liquids. The diffusion coefficients of [Fe(Cp)(2)](+) were smaller than those of Fe(Cp)(2) probably because of the coulombic interaction between charged species and the ionic liquids. The apparent heterogeneous rate constants of [Fe(Cp)(2)](+)/Fe(Cp)(2) in the ionic liquids were smaller than those in organic solvents. The heterogeneous rate constants correlate with the viscosity of the electrolytes probably due to the slow dynamics of the ions composing the ionic liquids.