A method for recovering oil from a subterranean formation is disclosed wherein an aqueous surfactant solution is injected into the formation to reduce the mobility of gas in a gas-flooding process. The gas may include hydrocarbon gas, inert gas, carbon dioxide, and steam. The surfactant is represented by the general formula ##STR1## where R is a linear or branched chain alkyl group with n carbon atoms wherein n ranges from 0 to about 18, except that if the gas is steam n ranges from about 9 to about 30;x ranges from 0 to about 20 and y ranges from 0 to about 20, provided x+y does not exceed about 20;R' is a linear or branched chain alkyl group with m carbon atoms wherein m ranges from 0 to 4, except that if the gas is steam m ranges from 1 to 4, with the proviso that the sum of x+y+m is at least one; andeach M.sup.+ is a cation.