Certain properties of concentrated solutions of indium trichloride, ranging in strength from 9.889 to 0.4070 m, have been investigated. These properties are: density, molar volume, specific and equivalent conductance, degree of ionization, ionization constant, relative viscosity, activities, and activity coefficients of solvent water and of solute. Two interesting results emerge,viz., the specific conductance passes through a maximum at 3.5 m, and, if the ionization of indium chloride is treated as that of a binary electrolyte, the expression α2c/(1 − α) is constant within 10% over the range 6.267 to 0.7363 m(13.90 to 2.122N).