Insecticidally, arachnicidally and fungicidally active novel isoxazolidines of the formula ##STR1## in which n is 2 or 3,R.sup.1 is H or alkyl,R.sup.2 is optionally substituted alkyl, cycloalkyl, alkenyl, alkinyl, aryl or a heterocyclic radical which is optionally substituted, andA is a di- or trivalent aryl or heteroaryl radical which is optionally substituted by alkyl, cycloalkyl, aralkyl, alkoxy, alkylthio, aryloxy, arylthio, halogen, CN, OH, halogenoalkyl, halogenoalkoxy, halogenoalkylthio, alkoxyalkyl, optionally halogen-substituted methylenedioxy or ethylenedioxy.Some of the intermediates are also new.