Two nerve activities of imidacloprid analogs with various substituents at the 5-position of the pyridine ring were measured: the conduction blockage in the excised central nerve cord of the American cockroach, and the binding inhibition of a radioligand, [3 H]imidacloprid, to the membrane preparation of housefly-head homogenates. Neuroblocking activity was quantitatively analyzed using physicochemical substituent parameters. The greater the electron-releasing resonance effect, the higher the activity. The introduction of sizable and alkoxy substituents was unfavorable. The nerve-binding activity of the tested compounds was linearly related to the neuroblocking activity with one exception. The higher the binding activity, the higher the blocking activity.