Traveller's diarrhea (TD) is the health problem most frequently encountered by tourists. Neither pretravel advice nor probiotica has shown a consistent prophylactic effect. Antibiotic chemoprophylaxis reduces the incidence of TD by 80-90% but should be recommended only to certain high-risk groups. Vaccination induces only short and partial protection. Standby treatment of TD with rehydration, loperamide and a flouroquinolone is recommended for travellers to most of the high-risk areas of the world.