The chemistry of the two-electron reduction product of viologen (1,1'-dialkyl-4,4'-bipyridinium, V2+.) neutral species, is important in understanding the electrochemical behavior of viologens and their utilization. The kinetics for the reactions of neutral methyl viologen (V-0) in the presence of H+ (from HCl), CH3COOH (pK(a) = 4.75), ClCH2CH2COOH (pK(a) = 4,00), HCOOH (pK(a) = 3.75) in aqueous media was examined by cyclic voltammetry according to the EEC, mechanism. To avoid the electrodeposition of V-0, we used a 9.1 (v/v%) H2O + DMF mixture as the solvent medium. To evaluate the rate constants for the chemical reaction followed by the second electron transfer step of V2+. the ratio of the anodic and cathodic peak current (I-pa2/l(pc2)) corresponding to V-0-e(-) reversible arrow V.+ was plotted against log tau, where tau is the time between E-1.2 and the switching potential, at various scan rates of 0.02-3.5 V s(-1). The chemical reaction was found to be a parallel reaction consisting of H+-catalyzed and general-acid (HA) catalyzed reactions. The second-order rate constants are determined as k(H+) = 3.5 x 10(3) M-1 s(-1), k(CH3COOH) = 5.7 M-1 s(-1), k(HCOOH) = 4.6 x 10(1) M-1 s(-1), and k(ClCH2CH2COOH) = 3.2 X 10(1) M-1 s(-1) using the Nicholson-Shain method and F-H2O was estimated as < 3 x 10(-6) M-1 s(-1). The CVs were digitally simulated under the assumption of a two-step reaction of V-0 following the two-step electrode reactions of V2+ to V-0. The simulated CVs show good agreement with those obtained experimentally, when the first-step reaction of V-0 is a relatively fast reversible reaction and the second-step reaction is a slow irreversible one. Based on these results, we propose that V-0 is in pseudo-equilibrium with H+ or HA to produce VH+ which undergoes a reaction with H2O.