Contact glow discharge electrolysis of acetonitrile solution containing a variety of aromatic compounds was carried out. A stable discharge was sustained around a platinum wire anode in contact with a surface of solution, when a d.c. high voltage over 500 V was applied between the anode and cathode immersed in the solution under ambient pressure of argon. An aromatic substitution involving radicals produced through the homolytic dissociation of acetonitrile significantly occurred to result in the formation of corresponding cyanoaromatics as well as propionitrile, succinonitrile, and acrylonitrile. The effects of reaction conditions on the current yields of products were discussed in association with the reaction mechanism.