Deposition of alternating layers of phosphomolybdic acid, PMo12, and generation-4 polyamidoamine dendrimer, PAMAM, on a gold electrode is demonstrated. The gold is first coated with a self-assembled monolayer of 4-aminothiophenol. Based on the charge under cyclic voltammetric peaks, at least 12 layers of PMo12 are deposited with an estimated quantity of 5.2 x 10(-11) mol cm(-2) in each. The voltammetry of PMo12 is consistent with that for solution studies, in that three two-electron processes are observed with formal potentials of 0.381, 0.238 and 0.012 V. However, the dependence of peak current on scan rate is indicative of redox surface-confined species. The PAMAM provided a spacer that led to a multilayer assembly with high conductivity and, because of its size, apparently high permeability. Regarding the latter, efficient catalysis of the reduction of nitrite and the oxidation of arsenite is achieved.