The vinyl polymerization of acrylonitrile initiated by the redox system Mn3+-glucose has been studied in aqueous sulfuric acid at 30–50°C. The rate of polymerization, the rate of Mn3+disappearance, etc. were measured. The effect of certain water miscible organic solvents, inorganic salts, dyes, solvent composition, solid substances, and inhibitors on the rate of polymerization has been investigated. Based on the experimental results, a suitable reaction mechanism involving the formation of a complex between Mn3+and the substrate molecule, whose decomposition yields the initiating free radical with the polymer chain being terminated by the mutual combination of growing chains, has been suggested.