Abstract: Aqueous concentrates of alkali metal salts of .alpha.-sulfonated fatty acid alkyl esters (ester sulfonate salts) which are pumpable at temperatures of at least 60.degree. C. are obtained without the addition of viscosity regulators by preparing pastes containing at least about 60% by weight of ester sulfonate salts derived from C.sub.16 and/or C.sub.18 fatty acids. More particularly, the concentrates contain less than 10 mole % of ester sulfonate salts with fatty acids containing fewer than 16 carbon atoms. The concentrates are obtained by neutralizing the crude ester sulfonates with concentrated alkali hydroxide solution with intensive cooling at temperatures of at most 90.degree. C.