Polymer was formed by an electrolytically initiated reaction in solutions of acrylonitrile and other monomers in dimethylformamide saturated with sodium nitrate. From analysis of copolymer compositions it was established that the polymer was formed at the cathode by an anionic propagation mechanism. The nature of the chain initiating step was investigated through polarographic measurements. These clearly suggest that chain initiation proceeds via direct electron addition to the double bond. A close correlation between the tendency to form anionic polymer and the polarographic potentials is indicated. The effects of current, time, and monomer concentration on the production of polymer were delineated. The yield of polymer increased linearly with time at fixed current density and showed first order dependence on monomer concentration. The absolute current efficiencies were extremely high and ranged to over 3 polymer molecules formed per electron transferred at the electrode. The molecular weights of the polymers are remarkably independent of monomer concentration, rate, and current density. A reaction scheme is proposed which postulates chain transfer to monomer. A kinetic analysis confirms the consistence of the scheme with experimental findings. Coloration and crosslinking found in some of the polymers are interpreted, and a mechanism is proposed.