The most common health problem encountered in international travellers to topical and subtropical areas is diarrhoea. Even though it is not a life-threatening condition, it may influence deeply the quality of a vacation or the success of a business trip. The majority of cases of travellers' diarrhoea are due to bacterial pathogens, but viruses have also been implicated in a minority of patients. It is advocated that travellers with diarrhoea provide themselves with sources of salt (crackers or soup) and mineral water, to prevent and treat dehydration. Otherwise, treatment recommendations follow illness severity. For mild cases, symptomatic relief alone can be recommended. Loperamide is an effective agent improving diarrhoea and associated symptoms. For moderate diarrhoea (requiring a forced change in itinerary) combination therapy is advised using a fluoroquinolone together with loperamide. Severe diarrhoea [fever > 38 degrees C, dysentery (bloody stools) or incapacitating symptoms] should prompt the voyager to take an antibiotic alone for 3 to 5 days. Loperamide is relatively contraindicated in these cases. For the minority of patients receiving chemoprophylaxis to prevent travellers' diarrhoea, fluoroquinolones taken once a day while in the area at risk produce the highest protection rate (up to 95%). However, most authorities do not recommend routine prophylaxis for travellers.