Two new Huckel equations have been determined for the activity coefficients (gamma) of BaCl2 in aqueous solutions at T = 298.15 K. One of these equations is a two-parameter equation with parameters B (related closely to the ion-size parameter in the Debye-Huckel theory) and b(1) (the coefficient of the linear correction term in Huckel equation where ln(gamma) is presented vs. the molality). It can be used up to an ionic strength (= I-m) of 2.0 mol . kg(-1). The other is a three-parameter Huckel equation with parameters B, b(1), and b(2) (the coefficient of the quadratic correction term in extended Huckel equation), and it applies up to the saturated solution where I-m is 5.3652 mol . kg(-1). The two BaCl2 parameters for dilute solutions were evaluated from the isopiestic data of Robinson (1940) [4]. These new parameters were tested with all isopiestic and galvanic cell data available in the literature for this investigation. The electrochemical data measured by Tippetts and Newton using two-phase barium amalgam cells (Tippetts and Newton, 1934) [16] show that the new parameter values apply without any changes in the best case up to I-m of 3.0 mol . kg(-1) at temperatures from (273 to 333) K. For more concentrated solutions at T = 298.15 K, new values of b(1) and b(2) for the extended Huckel equation were obtained from all points up to the saturated solution in the isopiestic set of Robinson (1945) [21]. The tests of the new parameter values were carried out with the existing electrochemical, vapor pressure, isopiestic, and solubility data available for these stronger BaCl2 solutions together with the existing values for the thermodynamic properties of this salt and its hydrates. Reliable activity and osmotic coefficients for BaCl2 solutions can be solved by using the new Huckel and extended Huckel equations. The values from these equations are tabulated here at rounded molalities and they were compared to the literature values. (C) 2014 Elsevier Ltd. All rights reserved.