Following the 1991 Gulf War, a number of soldiers who fought there began to complain of various symptoms and disorders, the collection of which came to be known as Gulf War syndrome (GWS). A debate has raged about the nature and cause of this illness, with many suggesting that it is a psychiatric condition. GWS continues to be a contested illness, yet there is no disputing that many Gulf veterans are ill. This article considers the way in which GWS sufferers understand their illness to be physical in nature and the way in which they negotiate and resist psychological theories of their illness. Based on 14 months of ethnographic fieldwork in the United Kingdom, data for this article were collected mainly by in-depth, semistructured interviews with GWS sufferers, their family members, doctors, and scientists, as well as healthy Gulf veterans. A total of 93 informants were interviewed, including 67 UK Gulf veterans, most of whom were ill. The paper argues that despite the increasing presence of psychiatry in military discourse, GWS reveals the way that people are able to transform, negotiate and even negate its power and assumptions.