Abstract One major legacy of the bacteriological revolution of the later nineteenth century is a simplified model of cause and effect. Looking back, this model seems entirely appropriate for a century dominated by infectious diseases. In this widely accepted picture of the nineteenth-century mortality experience the leading role is taken by the cholera epidemics which invaded Britain between 1831 and 1866. Historians have followed this lead by making cholera an exciting cause of political and social change, including the first Reform Bill. This essay suggests that the sporadic incursions of cholera were less a spur to reform than a distraction from the perpetual, or endemic, causes of death, which are inevitably those with the closest connections with the social, economic and political contexts of Victorian Britain. The Benthamite sanitarians built their case primarily on what they called continued fever, which we now identify as typhus and, increasingly, typhoid. The endemic diseases, year upon year, caused more deaths than cholera, and it is they which provided the quantitative definition of excess mortality which came to justify government intervention. Similarly, a further phase of public health reform was necessary after cholera was no longer a factor. These later reformers deplored the degeneration and mortality associated with extreme urbanization, and attributed them to respiratory conditions, fluxes, and what we might now call the pneumonia-diarrhoea complex among children. Cholera was an important phenomenon, but its effects on society need to be defined with some precision. Note: this is a revised version of the 12th Henry Cohen History of Medicine Lecture, given in 1983, and republished by kind permission of the Liverpool Medical Institution.