Aqueous solubilities of methane at 25°C have been determined in single-salt solutions equilibrated with a CH 4 gas phase at 350, 550, and 750 psia. Measurements were made over a range of ionic strengths in NaCl, KCl, CaCl 2, MgCl 2, Na 2SO 4, K 2SO 4, MgSO 4, Na 2CO 3, K 2CO 3, NaHCO 3, and KHCO 3 aqueous solutions. At 25°C and constant pressure and methane fugacity, methane solubilities were largely controlled by the stoichiometric ionic strength, I, and the cation of the salt. Except for an increased salting-out due to HCO 3 −, the anion effect was relatively insignificant. Different but consistent solubility trends were followed in monovalent and divalent cation salt solutions as a function of I. Solubilities increased in salt solutions having a common anion in the following cation sequence: Na + < K + ⪡ Ca 2+ < Mg 2+. The molal salting coefficient, k m , for each salt was constant under the experimental conditions of the study, k m is defined by log γ ch 4 I where γ ch 4 , the molal activity coefficient, is the methane solubility ratio ( m H 2O m salt solution ) measured at constant temperature, pressure, and CH 4 fugacity. Single-salt k m values are as follows: 0.121, NaCl (4m); 0.121, Na 2SO 4 (1m); 0.118, Na 2CO 3 (1.5m); 0.146, NaHCO 3 (0.5m); 0.101, KCl (4m); 0.108, K 2SO 4 (0.5m); 0.111, K 2CO 3 (2m); 0.145, KHCO 3 (0.5m); 0.071, CaCl 2 (2m); 0.063, MgCl 2 (2m); and 0.066, MgSO 4 (1.5m) where the molalities in parentheses refer to the maximum salt concentrations used in this study.