Travel-related health problems such as febrile illness have been reported in many travelers going to developing countries. With the emergence of new infectious diseases occurring in many parts of the world and their spread worldwide, early diagnosis of emerging infectious diseases or tropical diseases has become a very important part of controlling these diseases. In doing so, the itinerary of the ill returning traveler is crucial to formulating a differential diagnosis because exposure to pathogens differs depending on the area of travel. With up-to-date information on infectious diseases occurring worldwide, a differential diagnosis can be made by adding information on duration of travel, incubation period, underlying medical illness, history of prophylactic vaccines received, and knowledge of the patient's exposures during travel including insect bites, contaminated food or water, or freshwater swimming. Some travelers may have specific symptoms and signs such as fever, rash, or hemorrhagic manifestations. For example, eosinophilia suggests a possible helminth infection. In this article, the general approach to returnning travelers with suspected tropical disease will be described.