Novel sulfonylurea compounds containing a selenoalkyl substituent such as N-[[4-methoxy-6-(methylselenyl)pyrimidin-2-yl]aminocarbonyl]-2-methylsulfo nylbenzenesulfonamide and N-](4-methoxy-6-methyl-1,3,5-triazine-2-yl)aminocarbonyl]-2-methylselenylb enzenesulfonamide, suitable agricultural compositions containing these compounds, and their method-of-use as pre-emergence and post-emergence herbicides or plant growth regulants are disclosed.