The toxical potentiality of the cyanic radicle and the detoxicating characteristic of the amide group are studied following the evolution of the benzonitrile and benzamide toxicity when a cyanic or amide radicle is added to the original molecule. This comparative study shows that the presence of amide group has not always given a higher toxicity to the organic molecules that own it. It is the respective localization of the cyanic or amide radicles which appears to play the most important role.