Electrical conductivity of glasses from the system 0.40Li(2)O.0.60(xB(2)O(3)(1 - x)Si2O4) (0 less than or equal to x less than or equal to 1) were measured by impedance spectroscopy. The influence of the substitution of the first glass former by the second in electrical conductivity and in the parameters of the Arrhenius expression, i.e., activation energy and pre-exponential factor, is discussed. The electrical conductivity increases from the silica to the boron oxide region, with an anomaly at x = 0.3 but with no evidence of a mixed glass-former effect. The relaxation frequency, which is an intrinsic characteristic of each glass sample and is independent of geometrical parameters, was also deduced from impedance diagrams and are also presented for all compositions. (C) 2004 Elsevier B.V. All rights reserved.