Two series of room temperature ionic liquids, 1-alkyl-3-methylimidazolium tetrafluoroborate and 1-alkyl- 3-methylimidazolium bis(trifluoromethylsulfonyl)imide (n = 2―4) as electrolytes were prepared and fundamental electrochemical properties of the neat ionic liquids and those mixed with an organic solvent (EC-DMC-DEC, 1:1:1, mass ratio) were investigated. It was found that the Arrhenius equation is approximately fit for the relationship between conductivity and temperature for neat ionic liquids within lower temperature range (298―323 K). The VTF interpretation describes the conductivity temperature dependence for the ionic liquids containing tetrafluoroborate anion more accurately than those containing bis(trifluoromethylsulfon- yl)imide anion within wider temperature range. The potential windows are approximately 4.0 V for all these ionic liquids. Conductivities of the mixed electrolytes show a maximum value as the solution concentrations increase.