The nucleophilic substitution reaction of 2,4-dinitrofluorobenzene (DNFB) dissolved in the nitrobenzene (NB) phase by OH- in the water (W) phase has been studied using polarography and cyclic voltammetry at the polarized NB\W interface. A negative current observed in the polarogram is ascribed to the transfer of 2,4-dinitrophenolate (DNP-) ions formed after the substitution reaction of DNFB with OH- in the vicinity of the interface. Contrary to the case of micellar catalysis, the monolayer of cetyltrimethylammonium (CTMA (+)) formed at the NB\W interface has no appreciable catalytic effect on the substitution reaction. The most probable mechanism is the partition of DNFB to the W phase and the subsequent chemical reaction in W, which may be followed by the transfer of DNP- ions from W to NB, depending on the applied potential across the interface.