Novel benzylsulfonamide compounds containing ortho-heterocyclic substituents such as N-[(4,6-dimethoxypyrimidin-2-yl)aminocarbonyl]-2-[5-(methylthio)-1,3,4-oxa diazol-2-yl]benzenemethanesulfonamide are useful as preemergent and/or postemergent herbicides or plant growth regulants.