In September 1833 the medical officers of the Aldersgate-Street Dispensary, the oldest charitable institution of its kind in London, collectively resigned their posts in protest at a change in election procedures. This event elicited a widespread and vociferous reaction from medical practitioners throughout the British Isles as meetings were held and resolutions passed in support of the actions of the Dispensary's medical staff. This article seeks to make sense of this incident and the furore it generated, proposing that it reveals a fundamental transformation in the cultures of early nineteenth-century medicine and epitomises the newly imagined relationships between knowledge and social authority which were characteristic of the 'Age of Reform'. It suggests that during the early nineteenth century, a large number of medical reformers, many of them followers and readers of Thomas Wakley's radical journal, The Lancet, began to question the imperatives of gratuitous, charitable medical service. Where once the values of charity and benevolence had been central to the social performance of medical identity, early nineteenth-century medical radicals were increasingly figuring charity as an ignoble affront to a social authority based on knowledge and expertise rather than wealth or connections. In addition, this article also considers how the Aldersgate incident served to galvanise the semantic and conceptual existence of the medical 'profession'. Drawing upon the work of Benedict Anderson it demonstrates how medical societies and medical journals, especially The Lancet, encouraged medical practitioners to think of themselves as constituent members of a spatially extensive 'imagined community'. © 2009 The Author. Published by Oxford University Press. All rights reserved.