Acylated phenylaminotetrahydro-2-furanones of the formula ##STR1## in which R is C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -alkoxy or halogen,R.sub.1 is hydrogen, C.sub.1 -C.sub.3 -alkyl, C.sub.1 -C.sub.4 -alkoxy or halogen,R.sub.2 is hydrogen, C.sub.1 -C.sub.3 -alkyl or halogen,R.sub.3 is hydrogen or methyl, with the total number of C atoms of the substituents R, R.sub.1, R.sub.2 and R.sub.3 in the phenyl ring not exceeding 8,R.sub.4 and R.sub.5 independently of one another are hydrogen or methyl, andR.sub.6 is a C.sub.1 -C.sub.4 -alkyl group unsubstituted or substituted by halogen, thiocyano, cyano, C.sub.1 -C.sub.4 -alkoxy or C.sub.1 -C.sub.4 -alkylthio, or R.sub.6 is a C.sub.2 -C.sub.5 -alkenyl or C.sub.3 -C.sub.7 -cycloalkyl group each unsubstituted or mono- or polysubstituted by halogen, or R.sub.6 is a phenyl or benzyl group each unsubstituted or substituted by halogen, nitro, C.sub.1 -C.sub.4 -alkyl or C.sub.1 -C.sub.4 -alkoxy, or R.sub.6 is a 5- or 6-membered heterocyclic radical unsubstituted or substituted by methyl,have a systemic action, are suggested as novel microbicides. They can be used in the form of pesticidal compositions in particular for combating phytopathogenic fungi, or for preventing fungus infections on cultivated plants.