Novel adducts of a carbamoyl sulphoxide and urea having the formula ##STR1## and adducts of the said carbamoyl sulphoxide and an organic compound having the grouping ##STR2## wherein R is substituted or unsubstituted aryl, alkyl or alkenyl; R.sub.1 and R.sub.2, which may be the same or different, are H, substituted or unsubstituted alkyls, alkenyls or aryls, or aliphatic groups that, bound to one another in the form of a chain --(CH.sub.2).sub.p --(X).sub.n --(CH.sub.2).sub.q -- (in which p = 1,2,3; q = 1,2,3; X is O, S, SO, SO.sub.2 ; n = O or 1), form with N a ring when n = 1 and (p+q) .ltoreq. 4, and y is O, S or N- are contemplated. The adducts have herbicidal properties and herbicide compositions containing the adducts as well as a process for inhibiting the growth of plants or for destroying them with a herbicide containing the adduct are also contemplated.