The invention relates to novel pyrimidine derivatives of the general formula ##STR1## wherein A is phenyl, phenoxyphenyl, phenylthiophenyl, biphenyl or naphthyl R.sub.a, R.sub.b and R.sub.c are each independently hydrogen, halogen, cyano, nitro, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy, C.sub.1 -C.sub.4 haloalkyl or C.sub.1 -C.sub.4 haloalkoxy andX is one of the following bridge elements ##STR2## in which formulae R.sub.1 and R.sub.2 are each independently of the other hydrogen, C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 haloalkyl or CH.sub.2 O--C.sub.1 -C.sub.4 alkyl, R.sub.4 is hydrogen, C.sub.1 -C.sub.4 alkyl or CH.sub.2 OH and R.sub.3, R.sub.5 and R.sub.6 are each independently hydrogen or C.sub.1 -C.sub.4 alkyl,and to the acid addition salts thereof.The novel compounds possess microbicidal properties and are suitable in particular for controlling phytopathogenic microorganisms.