A central theme in both medical sociology and health psychology is how people make sense of their symptoms. Both literatures, despite their stress on different aspects of the health evaluation process, see illness in terms of matching present symptoms to an underlying understanding of illness. In this paper we argue that such accounts have difficulty in explaining the impact of contextual factors on how symptoms are evaluated. We therefore propose a model based on self-categorization theory (Turner, Hogg, Oakes, Reicher & Wetherell, 1987). It is proposed that symptoms are evaluated, not against pre-existing illness representations, but by reference to their impact on situationally salient identities. In support of this an experiment is described which involves students who are training to be physical education (PE) teachers. They are defined either in terms of a 'PE student' identity or in terms of a 'gender' identity and asked to evaluate a number of scenarios which describe different illnesses and injuries. Overall, the results provide clear evidence that the significance ascribed to scenarios depends on which identity is salient and hence indicate the viability of a self-categorization theory approach to symptom evaluation.