The mean ionic activity coefficients of aqueous 1-butyl-3-methylimidazolium bromide ([BMIm]Br) solutions in the concentrations ranging from 0.008 to 0.215 mol.kg(-1) were determined using potentiometric measurements at T= 308.15, 318.15, and 328.15 K. The obtained experimental data were correlated using the Pitzer and several local composition models, such as the non-electrolyte Wilson-NRF (N-Wilson-NRF), electrolyte Wilson-NRF (E-Wilson-NRF), electrolyte Wilson (E-Wilson), electrolyte NRTL (E-NRTL), modified electrolyte NRTL (ME-NRTL), and electrolyte NRTL-NRF (E-NRTL-NRF) models. The Pitzer parameters obtained were used to calculate the osmotic coefficients and excess Gibbs free energies of the solutions being studied. The results indicate that in general all the models used here can be successfully applied to predict the mean ionic activity coefficients of the aqueous ionic liquid solutions. However, the average standard deviations of the fit show that the NRTL based models represent the mean ionic activity coefficients with better precision. (C) 2017 Elsevier Ltd.