The conductance of ter-BuEt3NI, sec-BuEt3NI, iso-BuEt3NI,n-BuEt3NI and Bu4NI in toluene acetonitrile mixtures has been measured. The range of dielectric constant of the solvent mixtures covered from 9,4 to 35,9. The densities and viscosities of the solvent mixtures were also determined. The phoreograms of the ter-BuEt3NI and sec-BuEt3NI in the mixtures having molar fractions of toluene of 0,4, 0,5 and 0,6 and those of the iso-BuEt3NI and Bu4NI in the molar fractions 0,3, 0,4 and 0,5 show similar shape. The phoreograms lie below the Onsager limit line. The conductance data for the salts having asymmetric cations were analyzed using the Fuoss Onsager equation for unassociated 1–1 electrolytes. The data for the saltn-BuEt3NI in mixtures of mole fraction 0,1, 0,2 and 0,4 of toluene were fitted to the equation. All other systems studied did not fit. This investigation suggests that the geometry of the hydrocarbons chains has an effect on the conductance behaviour of ammonium salts.