The industrialization and urbanization of Britain during the 19th century gave the medical profession something to think about. In particular, were the radical changes taking place in society responsible for the sudden rise in endemic and epidemic disease? This article (part of the Science in the Industrial Revolution series) examines the reactions of two key figures in the history of British public health, James Philips Kay and Thomas Southwood Smith, to this question. Their outlooks typify the tendency of Victorian medical practitioners to construct economies of health that saw disease as a consequence of the violation of natural laws and cycles rather than as a product of industrial modernity.