Travel to the developing world by U.S. citizens has been increasing. Exposure to illnesses such as travelers' diarrhea, malaria, and vaccine-preventable diseases challenges the internist to provide pre-travel advice. Each traveler's itinerary, duration of stay and medical history, including previous immunizations, should be reviewed. Immunizations that may be required by individual countries, such as yellow fever and cholera, may then be administered. Immunizations for diseases such as hepatitis, typhoid fever, and meningococcal disease can be given according to the type of exposure within each country. Restricting a traveler's diet to cooked foods and purified, carbonated, or heated beverages may prevent travelers' diarrhea and other enteric infections. Most travelers will want to carry medications to treat diarrhea promptly. Malaria is prevented by avoiding mosquitos, taking safe and appropriate anti-malarials and treating malaria if it occurs. Preparation before travel may prevent medical complications.