N-Sulphenylated biurets of the formula ##STR1## in which R.sup.1 represents a trihalogenomethyl radical,R.sup.2 represents an optionally substituted aliphatic, cycloaliphatic, araliphatic or aromatic radical andR.sup.3 and R.sup.4 are identical or different and represent a hydrogen atom, an optionally substituted aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic radical or the amino or hydroxyl group, or together with the connecting nitrogen atom represent a five-membered or six-membered heterocyclic ring, the ring carbon atoms of which are optionally interrupted by one or more further hetero-atoms,which possess fungicidal activity.