A fungicidal synergistic mixture containinga) a compound of the formula I ##STR1## where the substituents have the following meanings: R.sup.1 is a phenyl radical which can carry one to three of the following groups: cyano, halogen, C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.2 -haloalkyl and C.sub.1 -C.sub.4 -alkoxy, ora pyrimidyl radical which can carry a C.sub.1 -C.sub.3 -alkyl group and/or a phenoxy group, the phenoxy group in turn being able to carry one to three of the following radicals: cyano, halogen, C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.2 -haloalkyl and C.sub.1 -C.sub.4 -alkoxy,A is oxygen or oxymethylene (--OCH.sub.2 --);X is CH or N,is oxygen or NR.sup.2, R.sup.2 being hydrogen, C.sub.1 -C.sub.3 -alkyl or C.sub.1 -C.sub.3 -alkoxy, andb) a pyrimidine derivative of the formula II ##STR2## where R is methyl, propyn-1-yl or cyclopropyl, in a synergistically active amount, is described.