AbstractN‐Mono‐ andNN‐disubstituted fluoracetamides have been tested as potential larvicides, contact insecticides and rodenticides.All monosubstituted amides were toxic to larvae ofMusca vicinaMacq. at a concentration of 100 p.p.m. Disubstituted amides were inactive or only slightly active. Only the amides monosubstituted by relatively small aryl radicals (phenyl,p‐tolyl,p‐fluorophenyl andp‐chlorophenyl) showed contact toxicity to adultMusca vicinaMacq. of a strain highly resistant to DDT.All compounds were toxic to laboratory rats. The approximate LD50values were lowest (4 to 8 mg./kg.) forN‐mono‐arylamides with small aryl radicals. Those with larger aryl substituents (α‐ and β‐ naphthyl,p‐diphenylyl andp‐bromophenyl) had somewhat higher LD50values. ThemolarLD50values of theN‐arylamides fall within a narrow range.The possible mode of action of