O-alkyl-O-[1,5-disubstituted-1,2,4-triazolyl-(3)]-thiono-phosphoric (phosphonic) acid esters and ester-amides of the formula ##STR1## in which R is alkyl of 1 to 6 carbon atoms,R' is alkyl, alkoxy or alkylamino of 1 to 6 carbon atoms or phenyl,R" is alkyl or cyanoalkyl of 1 to 4 carbon atoms or alkenyl of 3 or 4 carbon atoms,R'" is alkyl or cyanoalkyl with 1 to 6 carbon atoms in the alkyl radical, andX is oxygen or sulfur,which possess insecticidal and acaricidal properties.