Every year, millions of people travel abroad, exposing themselves to various diseases. Advice on risk avoidance and on self-medication is not always successful; sometimes travellers return home ill or become unwell soon afterwards. There are many possible causes for such illnesses, and physicians should try to establish whether the disease is specifically associated with the recent journey. The approach to assessment of the ill traveller should make use not only of signs and symptoms, but also of geography and epidemiology. Travellers with fever need immediate attention to rule out serious and potentially life-threatening conditions. Faced with a difficult diagnosis, physicians should consult with experts in tropical and travel medicine.