The electrochemical stability of selected redox active ions and molecules has been studied at temperatures around the melting point of the stoichiometric electrolyte by cyclic voltammetry. Tetrabutylammonium cation halide hydrates : (C4H9)(4)NX . nH(2)O (X = F, Cl, Br, 30 < n < 32) were selected as electrolytes. As in a liquid electrolyte, the highly charged form of a given redox couple is more stable, however this effect is more pronounced. No substantial shift of redox potential at temperatures around the melting point of the electrolyte is observed in the case of the Fe(CN)(6)(3-)/Fe(CN)(6)(4-) and Ru(NH3)(6)(3+)/Ru(NH3)(6)(2+) redox systems. This is not the case of Fc(CH2OH)(2)(+)/Fc(CH2OH)(2)(0) (Fc, ferrocene). At lower temperatures the direction of temperature dependence of the redox potential is similar, with the slope a few times larger than that observed in the liquid electrolyte. An interpretation of this effect based on the change in redox reaction entropy upon freezing of the electrolyte was proposed. The difference between the temperature dependence of the redox potential of the Fe(CN)(6)(3-)/Fe(CN)(6)(4-) redox system in tetrabutyl and tetramethyl cation hydrates was also discussed.