Measurements of AgCl solubility (in mol fraction units) in molten NaCl-AlCl3 and KCl-AlCl3 were determined by an electromotive force technique. For the NaCl-AlCl3 experiments, the temperature was maintained at 448 K and the composition of the solvent varied from X(AlCl3)solvent = 0.500 to X(AlCl3)solvent = 0.530. There was a compositional dependence of the AgCl solubilities with a minimum near the equimolar solvent composition. The minimum solubility in mol fraction of AgCl was 5.75 x 10(-3) at X(AlCl3)solvent = 0.505. The true solubility produce for AgCl at 448 K was calculated to be 7.35 x 10(-9). The magnitude of the solubility product is primarily related to the fact that the standard free energy of formation of NaAlCl4 from NaCl and AlCl3 is about 67 kJ mol-1 more negative than the corresponding free energy for AgAlCl4 (i.e., AgAlCl4 is unstable). In basic and in somewhat acidic melts, the solubility is related to the formation of the associated ionic species such as AgCl, AgCl2-, AgCl32-, and AgCl43-. From our measurements, the formation constant of AgCl at 448 K, K11, was 1.36 x 10(6). Further, the specific bond free energy for the associated complex AgCl, DELTAA11, has been calculated as -47.5 kJ mol-1. For the KCl-AlCl3 experiments, the composition was maintained at the equimolar and the temperature varied in the range 518 to 583 K. The AgCl solubility increases from 4.32 x 10(-3) at 518 K to 6.85 x 10(-3) at 583 K. The apparent heat of solution was 17.68 kJ mol-1 for this temperature range.