A process for preparing acetoacetarylamides of the formula I ##STR1## where R.sup.1 and R.sup.2 are identical or different alkyl radicals,l and m are each 0, 1 or 2, andis 0 or 1,by addition of diketene to the appropriate arylamine by continuously reacting the arylamine with diketene in the presence of a mixture of water and of a (C.sub.1 -C.sub.4)-alkanol at temperatures from 60.degree. C. to 100.degree. C. in the course of from 0.1 to 10 min.