The polymerization of maleic anhydride was investigated under constant current electrolysis in a simple H-type divided cell with 1,4-dimethylpyridiniumiodide as supporting electrolyte. The polymer formation depends on polymerization time, current intensity and on the nature of the supporting electrolyte. The polarographic measurements showed that the reduction potential of the supporting electrolyte is less than that of the monomer or the solvent. The product of the electrolysis arising from the supporting electrolyte initiates the polymerization. The mechanism of polymerization is assumed to be an anionic one.