This thesis is a historical, qualitative case study of the emergence and disappearance of telegraphists’ cramp in the British Post Office between 1875, when it was first reported, and 1930, by which point it was in decline. Telegraphists’ cramp was an occupational disease that has attracted little attention from social historians, and references in occupational health history are scarce, possibly because of the relatively short lifespan of the disease. Telegraphists’ cramp was initially categorised with related occupational diseases (for example writers’ cramp) as a curiosity with little further information about causation, signs and symptoms apart from the label associating it to the work of the telegraphist. It subsequently acquired much greater prominence owing to political factors. When telegraphists’ cramp appeared, trade unions were developing throughout the Post Office and were challenging pay, grades and working conditions of the workforce, including effects on health. At the same time, wider interest was developing on the effects of the rapid industrialisation of society on workers’ fatigue and health. Consequently, telegraphists’ cramp became an important focus of medical research and government intervention. Moreover, telegraphists’ cramp is of particular interest as a disease because it emerged in response to the introduction of new technology, the Morse key, into an office environment, at a time when most other occupational diseases occurred in hazardous factory environments. My thesis is thus a study of telegraphists’ cramp as the first office based occupational disease. I have devised a two-stranded social-historical model to map the changing factors shaping telegraphists’ cramp through its lifecycle. First, I describe three stages in the evolution and decline of telegraphists’ cramp, using a human-centred approach where the individual (worker) response is at the heart of the model, situated in and influenced by a wider context of government sociopolitical initiatives e.g. legislation, medical and scientific knowledge theories and practices, and employer (organisational) actions. Secondly, drawing on Ludwik Fleck’s theories of thought collectives, I map the interactions between the expert and lay stakeholders involved with telegraphists’ cramp in response to changing medical, political and scientific knowledge and arguments during the lifecycle of the disease. This model provides a comprehensive social-historical account of the different phases in the emergence and decline of telegraphists’ cramp.