Furanyl-(2)-1,2,4-oxadiazoles of the formula wherein A represents an aromatic mononuclear or binuclear ring system which with two adjacent carbon atoms is fused with the furan nucleus in the manner indicated, R represents hydrogen, a lower alkyl group, an optionally substituted phenyl group, as well as an optionally functionally modified carboxy group, X represents a direct bond, as well as the following divalent radicals B represents a straight-chained or branched, optionally substituted alkyl group or an optionally substituted aryl or heteroaryl group.