Humans, animals and environment are continuously exposed to many toxic agents, whose some effects remain still unknown. To better understand and manage these toxicological problems, modern toxicology has developed a scientific methodology allowing to evaluate the risk related to these potentially hazardous substances. The present paper first defines the risk assessment and details its four main steps. Then, the role of the veterinarian in this methodology is considered. More acutely, his involvement in the management of the risks related to veterinary drugs and in the use of animals as bioindicators is reviewed.