peer reviewed ; The biological hazards posed by micro-organisms have lead to their categorisation into risk groups and the elaboration of classification lists. Current classification systems rely on criteria defined by the World Health Organization, considering the severity of the disease the micro-organism might cause, its ability to spread and the availability of prophylaxis or efficient treatment. Animal pathogens are classified according to the definitions of the World Organization of Animal Health whereby also economic aspects are considered. In Europe, classification is often directly linked to containment measures. The Belgian classification however, considers only the inherent characteristics of the micro-organism, not its use, making it independent of containment measures. Also a common list for human and animal pathogens is elaborated, allowing a comprehensive approach. Evolution of scientific knowledge requires regular updating of classification lists. This paper describes the particularities of the Belgian classification and the methodology that was used for its peer-reviewed revision, hereby focusing on animal pathogens.