In order to investigate the reactivity of carbanions in anionic polymerizations, oscillopolarographic measurements of oxidation potentials of polymer anions and arene anions were carried out in tetrahydrofuran solutions with sodium tetraethyl-aluminate as a supporting electrolyte. The oxidation potentials of the carbanions measured with a microplatinum electrode were expressed against the standard potential of naphthalene radical anion: phenanthrene−, 0 V; biphenyl−, 0 V; anthracene2−, 0.27 V; stilbene2−, 0.48 V; (polystyrene)2−, 1.26 V; [poly(α-methylstyrene)]2−, 1.13 V; (diphenyl-ethylene2)2−, 1.13 V, poly(4-vinylpyridine)2−, 1.75 V, fluorene−, 1.71V. There is a linear relationship between oxidation potentials and energy level of the highest occupied molecular orbitals of these carbanions, which were obtained from the Hückel molecular-orbital method. It was suggested that the oxidation wave was caused by direct electron transfer from carbanion to anode. The carbanion, which was reported to have a high reactivity for the initiation or propagation of anionic polymerization, exhibited a less noble oxidation potential. The electrolytic oxidation of disodium α-methylstyrene tetramer yielded an oligomer of high molecular weight, 1000, in anodic compartment. For the anodic reaction, it is proposed that one electron transfer forms radical species followed by radical coupling.