The presence of a disorganized octadecylsilane, C-18, monolayer on an indium-tin oxide (ITO) electrode has a profound effect on the electrochemistry of hexacyanoferrate, Fe(CN)(6)(3-/4-). We found that the alkylsilane monolayer forms a hydrophobic matrix, which affects the heterogeneous rate of electron transfer of the metallic complex, depending on the nature of the counter cation presence in the solution. A model is suggested which accounts for these effects as well as for the changes in the formal redox potential that are observed.