Fibromyalgia syndrome (FMS) is characterised by chronic widespread pain, tender points and fatigue. A clear biological explanation of FIVIS is lacking, and there is debate regarding the 'legitimacy' of the condition. Often, therefore, people with FIVIS do not obtain a straightforward, clear diagnosis - or any diagnosis at all. This research sought to explore the diagnostic and subsequent experience of people with FIVIS. Semi-structured interviews were conducted with 17 people formally diagnosed with FIVIS. Interviews were tape-recorded, transcribed, and analysed by the inductionabduction method. Findings were triangulated through documentary analysis of lay literature on FMS. Participants referred to their symptoms within a dualistic framework, with symptoms seen as an aggressive force that invades the body. Individuals had high expectations of the medical profession. They expected tests to be done, with a diagnosis and prognosis to follow. The diagnostic process was often reported as complex, ambiguous, and ambivalent. Although individuals were initially relieved following the diagnosis, this was often replaced by shock and uncertainty, as no one appeared to know what FIVIS is, what caused it or how to treat it. Consequently, informants had actively to search for a meaning of FMS through lay networks and literature. Several chose to reject the diagnosis, as it did not represent their own understanding and experience of their symptoms.The meaning attached to FIVISin fluenced participants' coping strategies. They had difficulty finding adequate social support, and while significant others assumed this role, the informants felt uncomfortable. Many expected the medical profession should provide social support, but this was not always forthcoming. People diagnosed with FIVIS expect their illness to be satisfactorily understood and explained by the medical profession. Tensions exist between this expectation and their actual experience.