Diarrhea, malaria, and viral hepatitis are among the preventable diseases of travellers. In Switzerland, almost all serious cases of malaria are introduced from tropical Africa; therefore, we recommend protection with 250 mg of mefloquin per week for this destination. Elsewhere, protection against mosquitoes, in combination with Fansimef for self-treatment, may be enough. For travellers' diarrhea, we prefer immediate treatment with ciprofloxacin or cotrimoxazol to prophylaxis. Administration of immune globulin against hepatitis A may be recommended for all non-immune tourists, whereas protection against hepatitis B is necessary for health workers and sex tourists.