The psychological and socio-cultural influences on the process of defining `disease' as an illness and the illness behaviour of a group of Chinese medical students were studied. Data were collected from a health diary done by second-year medical students of the University of Hong Kong. Symptom experience was frequent within the one-week period of study. Consultation with doctors was, however, low. Psychological state related symptoms were most common and were related to the intensity of academic work demands. Illness behaviour in the form of positive remedial action was related to the estimated severity of the symptoms and the anxiety experienced. Estimated severity and anxiety predicted a greater likelihood of talking to friends or relatives about the symptom, and of seeing a doctor. Subjects were also more likely to see a doctor when advised specifically to do so. A mixed pattern of Western and Chinese illness behaviours and remedies was noted. This is discussed in the context of the transitions in concepts of illness and health experienced by Chinese medical students trying to integrate their Western training with traditional Chinese thinking.