In the production of an aryl lactamhydrazone of the formula ##SPC1## In which A represents optionally substituted alkylene, aralkylene or cycloalkylene, each with up to 20 carbon atoms, and Q represents optionally substituted, mononuclear to trinuclear aryl or an optionally alkylsubstituted mononuclear or binuclear heterocyclic aromatic system with 1 to 3 hetero atoms, In which a lactim-ether of the formula ##SPC2## In which R is aryl or alkyl of 1 to 6 carbon atoms, Is reacted with an arylhydrazine or heteroarylhydrazine of the formula H.sub.2 N--NH--Q (III) the improvement which comprises effecting the reaction at a temperature of about -20.degree. to 150.degree.C and in the presence of at least a catalytic amount of acid, whereby the yield is markedly increased. Those compounds wherein A is --(CH.sub.2).sub.2-11 -- and Q is pyridyl or phenyl substituted by at least one nitro, sulfo, sulfonamido or carboxy group are new and exhibit fungicidal activity.