The behaviour of Ni(II) and Ni(0) has been studied in aqueous solutions of mixtures of LiCl and LiNO3 at chloride concentrations up to 14 M, by using combined techniques (d.c. and pulse polarography, double potential step chronocoulometry and chronopotentiometry). The kinetics of the reduction process is controlled by the chloride and free water contents. At constant water activity, reaction orders, with respect to chloride bulk concentration, are +1. At high chloride concentrations, Tafel plots yield two straight lines with respective slopes of 43 and 170 mV. The data are explained by assuming that the chemical reaction [Ni(H2O)6]+ + Cl−⇌[Ni(H2O)5Cl]+ + H2O precedes the bielectronic reduction with the apparent values of the transfer coefficients α→1=0.35 and α←2=0.4. Reoxidation of cathodically generated Ni(0) gives Tafel slopes, which are characterized by an apparent α of about 0.4, a very small water effect and a chloride reaction order of +1. These facts are explained by assuming that the rate determining step consists in the chloride-assisted electron abstraction Ni+Cl−-e→NiCl. A reaction mechanism is proposed, with the chloride ion acting as a catalyst and Ni +Cl− − e⇌NiCl as the slow step of the charge transfer process.