Objective: To document the organisational response of Furness General Hospital to the large outbreak of legionnaire’s disease in April 2002 and assess the contribution made by the hospital’s major incident plan. Method: Qualitative analysis of interview transcripts and written comments from some staff involved in the management of the incident. Documentary analysis of major incident plan and other written materials. Results: The incident posed considerable managerial and clinical problems and this paper describes how they were overcome. In particular, strategies for dealing with supply (of staff, beds, and resources) and managing demand (by liaising with primary care and the public) seem to have been successful. Many functions necessary for managing the incident were poorly dealt with in the plan, especially procedures for handling the news media and liaison with agencies outside the hospital. Lack of explicit guidance appeared not to hinder the organisational response. There may have been an unspoken high level decision to allow staff to draw on their skills and experience in improvising a response to the initial challenge and learning adaptively as the incident unfolded. There was also evidence that staff disregarded existing job and role boundaries and focused instead on tasks, working flexibly to ensure that these tasks were completed. Conclusions: Protracted major incidents pose particular management challenges and may benefit from an approach different from that set out in typical major incident plans. Staff must be able to act flexibly and responsively. Some form of checklist or toolkit may be preferable to a detailed plan for some types of incident.