After the influential writings of Ligniers (around 1900), the terms pasteurelloBis and haemorrhagic septicaemia tended to become synonymous. Nevertheless, it noon became clear that many infections with pasteurellas did not produce haemorrhagic septicaemia, and, conversely that many cases of haemorrhagic septicaemia in the pathological sense, were not caused by pasteurellas. This brought the term into disrepute, particularly in North America, where it had been extended to include shipping fever, a disease of complex and perhaps variable etiology. In tropical Asia and Africa haemorrhagic septicaemia (HS) denotes an acute infection, mostly of cattle and buffaloes, with high mortality in clinical cases which is uniformly caused by types 6B or 6E Pasteurella multocida. The disease can be defined in terms of the causative agent, so haemorrhagic septicaemia is a particular kind of pasteurellosis just as typhoid is a particular kind of salmonellosis. Apart from the pasteurellas, no other specific pathogen has been found in cases of haemorrhagic septioaemia. Pactors such as stress and minor infections have been postulated as precipitating causes. The disease in the field is adequately controlled by vaccines directed solely against the appropriate pasteurella and clinical cases, if treated in time, may be cured by chemotherapy aimed at this organism. If any other primary pathogen did exist it would need to have the same or wider geographical distribution as the pasteurella. The concept that haemorrhagic septicaemia in a specific kind of pasteurellosis was foreshadowed by Roberts (1947) and Ochi (1952) with more definite proof being adduced by Bain (1954)t Hudson(l954) and Dhanda, (1959). Much useful work on the disease and its prevention in India was done by Majors J.D.B. Holmes and F.S.H. Baldrey in the first decade of this century and their papers are worth consulting. Reviews on haemorrhagic septicaemia in more recent times are those by Vittoz (1952), Bain (1957, 1961); on pasteurellosis in general by Hudson (1959), Carter and Bain (1960) and Carter (1967). Reports of conferences on haemorrhagic septicaemia have been published by FAO (Report 19609 1962 and 1979).