Novel benzothiophene and benzofuran derivatives of the general formula I ##STR1## wherein X is oxygen or sulfur, R.sub.1 is hydrogen, halogen, C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 haloalkyl, R.sub.2 is hydrogen, halogen, C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.4 haloalkyl, R.sub.3 is hydrogen, C.sub.1 -C.sub.4 alkyl or halogen and R is a 4-cyano-3-pyrrole radical of which the N atom carries one of the following substituents:A: hydrogen or CO--R.sub.4 in which R.sub.4 is unsubstituted C.sub.1 C.sub.6 alkyl or C.sub.1 -C.sub.6 alkyl substituted by halogen or by C.sub.1 -C.sub.3 alkoxy; C.sub.3 -C.sub.6 alkenyl, C.sub.3 -C.sub.6 alkynyl, unsubstituted C.sub.1 -C.sub.6 alkoxy or C.sub.1 -C.sub.6 alkoxy substituted by halogen or by C.sub.1 -C.sub.3 alkoxy; C.sub.3 -C.sub.6 alkenyloxy, C.sub.3 -C.sub.6 cycloalkyl or tetrahydrofur2-yl;B: S-R.sub.5 in which R.sub.5 is C.sub.1 -C.sub.3 haloalkyl;C: CH(Y)R.sub.6 in which R.sub.6 is hydrogen or C.sub.1 -C.sub.8 haloalkyl and Y is hydroxy, halogen or OC(O)R.sub.7 in which R.sub.7 is C.sub.1 -C.sub.8 alkyl, C.sub.1 -C.sub.8 haloalkyl, C.sub.2 -C.sub.6 -alkenyl, 2-tetrahydrofuryl, 2-tetrahydropyranyl or C.sub.1 -C.sub.6 alkoxycarbonyl;D: CH.sub.2 -Z in which Z is one of the groups ##STR2## wherein R.sub.8 and R.sub.9 are each, independently of the other, hydrogen, unsubstituted C.sub.1 -C.sub.6 alkyl or C.sub.1 -C.sub.6 alkyl substituted by cyano or by C.sub.1 -C.sub.6 alkoxycarbonyl; C.sub.3 -C.sub.6 alkenyl, C.sub.3 -C.sub.6 alkynyl, C.sub.3 -C.sub.7 cycloalkyl, unsubstituted phenyl or phenyl substituted by halogen, by C.sub.1 -C.sub.6 alkyl, by C.sub.1 -C.sub.6 haloalkyl and/or by C.sub.1 -C.sub.6 alkoxy, with the proviso that only R.sub.8 or R.sub.9 may be hydrogen; R.sub.10 and R.sub.11 are each, independently of the other, hydrogen, C.sub.1 -C.sub.6 alkyl or C.sub.1 -C.sub.6 alkoxycarbonyl; R.sub.12 and R.sub.13 are each, independently of the other, hydrogen, C.sub.1 -C.sub.6 alkyl or C.sub.1 -C.sub.6 alkoxycarbonyl; and R.sub.15 is oxygen, sulfur, >C.dbd.0 or >N--R.sub.14, wherein R.sub.14 is hydrogen, C.sub.1 -C.sub.6 alkyl, formyl, C.sub.1 -C.sub.6 alkanoyl or C.sub.1 -C.sub.6 alkoxycarbonyl; and n is one of the numbers 0 or 1.The novel active ingredients serve to control harmful microorganisms, especially phytophathogenic fungi. They can be used together with suitable formulation adjuvants in the form of compositions, and are suitable also for preventing attack on cultivated plants by harmful microorganisms.