Measurements have been made to determine the solubilities of ethane, C 2 H 6 , propane, C 3 H 8 , and carbon dioxide, CO 2 , in aqueous solutions of sodium cumene sulfonate (NaCS) at 25°C. The solubilities measured for each gas satisfy Henry's law at all concentrations of NaCS. The solubilities of C 2 H 6 and C 3 H 8 exhibit quite similar behavior with respect to added NaCS. The solubilities of these two gases are very low in pure water and are found to be nearly independent of NaCS concentration over a concentration range of 0–0.4 mol NaCS/kg H 2 O. At intermediate concentrations of NaCS, the solubilities of C 2 H 6 and C 3 H 8 exhibit a gradual increase with added NaCS concentrations ranging from 0.4 to 2.0 mol NaCS/kg H 2 O. At NaCS concentrations greater than 2.0 mol NaCS/kg H 2 O, the solubilities of these two gases increase with added NaCS in an approximately linear manner, with the solubility of C 3 H 8 increasing more rapidly than that for C 2 H 6 (by a factor of approximately 2.5). CO 2 is much more soluble in pure water than the hydrocarbon gases and exhibits markedly different behavior with respect to added NaCS. The solubility of CO 2 decreases with added NaCS over a concentration range of 0–0.9 mol NaCS/kg H 2 O, passes through a minimum at a concentration of approximately 1.0 mol NaCS/kg H 2 O, and then increases with added NaCS at higher NaCS concentrations in a manner similar to that observed with C 2 H 6 and C 3 H 8 . The trends in solubility observed for these three gases dissolved in aqueous solutions of NaCS resemble those found previously with aqueous solutions of ordinary surfactants. The solubility data measured for these three gases can be interpreted surprisingly well in terms of the mass-action model for micellization, in which salting-out effects due to monomer salt ions suppress gas solubility at low NaCS concentrations and gas solubilization by small micelles of NaCS acts to enhance gas solubility at the higher NaCS concentrations.