Technical Abstract: The genus Edwardsiella includes two species of bacteria that cause major diseases in fish: Edwardsiella tarda (1965) infects fish and other animals and Edwardsiella ictaluri (Hawke 1979; Hawke et al. 1981) infects primarily fish. A third species, Edwardsiella hoshinae (Grimont et al. 1980), infects birds and reptiles. Edwardsiella tarda produces the disease commonly known as fish gangrene, emphysematous putrefactive disease of catfish or red disease of eels and hereafter known in this text as Edwardsiella septicaemia (ES), and E. ictaluri causes ‘enteric septicaemia of catfish’ (ESC). Because E. tarda and E. ictaluri produce distinctively different diseases, they are discussed separately. The discussion of each of these diseases include aspects of the disease agent, geographical distribution and host range, economic importance of the disease, diagnostic methods, genome structure, pathogenesis and immunity, control, treatment and epizootiology and conclusions and recommendations for future studies.