Process for making secondary amphoacetate and amphodiacetate of the formula ##STR1## wherein R.sup.1 is C.sub.8 -C.sub.18 -alkyl or C.sub.8 -C.sub.18 -alkenyl, R.sup.2 is hydrogen or a group of the formula --CH.sub.2 COOM and M is alkaline or alkaline earth metal, which comprises heating a compound of the formula 2 ##STR2## at pH between 7-14, at a temperature of 80 to 90 deg C. and for at least 24 hours and subsequent reaction with an aqueous solution of chloroacetic acid or is alkali salt at a pH from 7 fo 14 and a temperature of 80 to 90.degree. C. Due to the long period for the ring opening in the first step predominantly secondary products are obtained which are advantageous in that they show a low viscosity of their aqueous solution.