Fungicidal nitro-substituted benzothiazolones of the formula ##STR1## in which R represents alkyl which is monosubstituted or disubstituted by identical or different substitutents from the group consisting of cyano, carboxyl, alkyl-carbonyl, alkoxycarbonyl, and alkylaminocarbonyl or and phenyl or phenylcarbonyl in each case optionally monosubstituted to pentasubstituted by identical or different substituents from the group consisting of halogen, alkyl, halogenoalkyl and alkoxy, or R is the radical --CONHR.sup.1, in which R.sup.1 represents alkyl which is monosubstituted or disubstituted by identical or different substituents from the group consisting of cyano, carboxyl and alkoxycarbonyl, andX represents hydrogen, halogen, alkyl or halogenoalkyl.