Stable, ordered films of myoglobin (Mb) and didodecyldimethylammonium bromide (DDAB) on electrodes were used to catalyze reductions of organohalides with significant lowering of activation free energy. Myoglobin in these films is made to act as a redox enzyme. Ethylene dibromide and trichloroacetic acid were dehalogenated by MbFe(II), with reaction rates much larger in the films than with MbFe(II) in solution. A highly reduced form of Mb was also produced in these films, and was used to dechlorinate tetra- and trichloroethylenes, All of these reactions occur at potentials about a volt more positive than the corresponding direct reductions at bare electrodes, Products were similar to those obtained from reduction by anaerobic bacteria or the enzyme cytochrome P450. Reactions proceeded for thousands of catalyst turnovers, and apparent rate constants were in the range 2 x 10(2) to 10(4) M(-1) s(-1) .Rates are partly enhanced by preconcentration of organohalides in the films. These ordered protein-surfactant films, featuring stacked surfactant bilayers, provide reaction environments resembling biomembranes.