A herbicide comprising the sulfonylurea derivatives of the formula (I): ##STR1## wherein Q is --CH.dbd.CH-- or --S--, R is C.sub.1-3 alkyl, and X is --OCH.sub.3 or --CH.sub.3 ; or a salt thereof, are useful for the control of undesired vegetation, for example, black glass (Alopecurus myosuroides) or downy brome (Bromus tectorum L.) in the presence of many valuable small grain cereals such as wheat, barley, oats and rye. The herbicide is also unexpectedly tolerant to small grain cereals such as wheat, barley, oats and rye.