A water-insoluble quaternary starch ether ester containing ester groups of the formulae --O--CO--CH.sub.3 and/or --O--CO--C.sub.2 H.sub.5 and other groups of the general formula IwhereX is a direct bond or --CH(OH)-- andA.sup.- is an anion or one equivalent of an anion, andR is hydrogen, methyl and/or ethyl,and the degree of substitution of said ether group being within the range from 0.002 to 0.8