Polymerization of adsorbed monomers at the water 1,2-dichloroethane interface was studied with a series of surface active derivatives of pyrrole. Polymerization was induced by an electron transfer reaction between a monomer dissolved in the organic phase and Ce(SO)(4) dissolved in the aqueous phase. The formation of a polymer layer at the interface was monitored by surface tension measurement and by cyclic voltammetry in the presence of transferable ions. It was found that in contrast to a simple adsorbed layer, an interfacial tension in the presence of a polymer layer becomes independent of the applied potential and that a polymer layer strongly inhibits ion transfer reactions.