The density, viscosity, refractive index, heat capacity, heat of dilution, ionic conductivity, and electrochemi-cal stability of 1-butyl-3-methylimidazolium bromide ([bmim][Br]), 1-butyl-3-methylimidazolium iodide ([bmim][I]), and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) were measured at room temperature or over a tem-perature range of 293.2 to 323.2 K. The density and refractive index values of [bmim][I] appeared to be the highest among three ionic liquids (ILs). However, the experimental viscosity values of [bmim][Br] were higher than those of [bmim][BF₄], while the heat capacities and heats of dilution of [bmim][BF₄] were higher than those of [bmim][Br]. The cyclic voltammogram of[bmim][br] and [bmim][BF₄] indicated electrochemical windows in the stability range from 2.7 V of [bmim][Br] to 4.7 V of [bmim][BF₄]