Blackleg is an acute, infectious, but not contagious gas oedema with an epizootic course. In general, young cattle and in some cases sheep and goats may become infected. Blackleg is a notifiable disease in Germany. Clostridium (C.) chauvoei is the causative agent of blackleg and must be separated from other gas oedema causing bacteria, especially C. septicum, the infectious agent of malignant oedema. Further Clostridium species have to be considered in differential diagnosis. Using traditional microbiological methods the discrimination of C. chauvoei from C. septicum is difficult as both organisms exhibit similar properties. Differentiation of isolates is possible by the examination of biochemical (fermentation) properties. Additional options to identify C. chauvoei are the use of direct immunofluorescence and PCR based detection methods.