Abstract: The invention provides herbicidal compositions containing as active ingredients (1) a 1,2,4-triazin-5-(4H)-one derivative of the general formula ##STR1## in which R is amino or isobutylideneamino, and (2) a phenoxyalkanecarboxylic acid of the general formula ##STR2## in which X is methylene or methylmethylene,R.sub.1 is chlorine or methyl andR.sub.2 is hydrogen or chlorine,Which may be in the form of a salt or ester thereof, alone or in admixture with a solid or liquid or liquefied gaseous diluent or carrier;Which combinations provide synergistic weed-killing action against a wide range of weeds in cereals.