For the production of solid, substantially anhydrous alkali metal salts of .alpha.-sulfofatty acid alkyl esters containing from 8 to 22 carbon atoms in the fatty acid chain and from 1 to 6 carbon atoms in the ester alkyl radical, solid or molten .alpha.-sulfofatty acid alkyl esters are simltaneously mixed with an aqueous solution of hydrogen peroxide or an H.sub.2 O.sub.2 -yielding compound and with solid alkali metal carbonate at a temperature of from 20.degree. to 80.degree. C. optionally in the presence of aqueous alkali metal hydroxide, the ratio by weight of ester of H.sub.2 O.sub.2 being from 1:0.01 to 1:0.06 and the molar ratio of ester to alkali metal carbonate being in the range of from 1:0.5 to 1:0.75, the foam formed through the release of CO.sub.2 is mechanically destroyed under a pressure of from 0.2 to 1.0 bar and at a temperature of from 50.degree. to 70.degree. C., and the product formed is residually degassed and residually dehydrated under a pressure of from 15 to 50 mbar and a temperature of from 50.degree. to 80.degree. C.