The reduction mechanism of 1-alkyl-2-cyanopyridinium (2(CN) +) and 1-alkyl-3-cyanopyridinium (3(CN) +) has been investigated in acetonitrile using dc, normal pulse (NP) and reverse pulse polarography (RP). The reduction of 2(CN) + at low concentraions (< 4 × 10 −5 M) and short pulse widths ( t p < 2 ms) leads to the formation of the radical 2(CN) in a reversible process with E°′ = −1028±2 mV. ▪ At longer times, dimerization of the radicals occurs at the 2-, 4- and 6-positions, leading predominantly to 4,4′- and 4,2′-dimers (all dimers denoted by D(CN) 2). ▪ Fast interconversion of linking positions takes place. 4,4′-Dimers are the predominant species. 2,4′-Dimers, although minor species, enable a path for one cyano group to be lost in a homogeneous reaction, resulting in a new pyridinium ion, D(CN) +. This pyridinium ions is reduced further at potentials more negative than 2(CN) +. ▪ ▪ Cyanide ions react with 2(CN) + to form 2,4-dicyano-1-methyl-1,4-dihydropyridine. ▪ The rate of this reaction is relatively slow in the presence of LiClO 4 ( k f = (8±0.5) s −1 M −1, k b = (2.3±0.2)×10 −3 s −1, log ( K/M −1)=(3.5+0.1)) and is much faster in TBAP. During the electrochemical reduction of 2(CN) +, during which cyanide ions are released, reaction (5) takes place, causing a decrease in the polarographic limiting current in TBAP, but not in LiClO 4. The reduction of 3(CN) + consists of a single charge transfer followed by irreversible dimerization. ▪