The multiplication of diagnoses, the seepage of diagnostic language into popular culture and the media, the rise of self-diagnosis and the world wide web, all position diagnosis as an important social phenomenon to which anthropology, sociology, and their cognate disciplines must pay particular attention. In order to understand the health goals to which individuals and communities aspire, it is important to know the place that diagnosis plays in understanding health and illness. In order to determine what conditions are of particular public concern, it is also vital to know how those conditions are conceptualised, categorised, and indeed, diagnosed. Whether it is fibromyalgia, gout, or obesity, each diagnosis is testimony to a particular way of seeing the world and understanding disease. Fibromyalgia, for example, is, as I write these words, a symptom-based diagnosis, established in the presence of a certain number of symptoms assembled in indicative ways. But, at the same time, it is a diagnosis which lacks legitimacy in the eyes of many, for the absence of biological markers providing so-called objective confirmation. This is why clinical researchers, and notably geneticists, are frenetically trying to discern a profile, be it genetic or biologic, which can explain this baffling condition. Gout is also determinant, but in other ways. It has biological markers, so its existence is not in doubt, but its causes and location raise questions. Does the problem of uric acid build-up in the joints belong to rheumatology, endocrinology or nephrology? Is it a disease of decadence, or one of poverty? Obesity, on the other hand, says much about who we are, and what a society should look like. In the neo-liberal context of responsibilisation, obesity, like gout, makes social statements about the large body, stigmatising at the same time as it rings alarm bells about the society in which the large individual is situated. The health of a nation is measured in BMI, with rising obesity touted as an alarming trend.