The risk of malaria poses travellers and their advisers with difficult problems as drug resistance spreads worldwide. Protection against infection rests on travellers' knowledge of the risk of malaria, on their avoidance of malaria vectors and on their compliant use of chemoprophylaxis. In this article, Robert Ste f fen and Ronald Behrens explain that one of the priorities for reducing malaria morbidity is to improve travellers' use of personal protection against mosquito bites. They show that none of the drugs, or combinations thereof, provide a 100% efficacy, owing to increasing drug resistance, mainly of Plasmodium falciparum. The commonly used drugs for malaria prophylaxis (mefloquine, doxycycline, chloroquine and proguanil) often cause minor side effects. All, except proguanil, have also been occasionally associated with severe adverse effects. Other drugs (pyrimethaminelsul fadoxine, amodioquine) are not suitable for chemoprophylaxis because of unacceptable adverse reactions. The use of drugs for self therapy is constrained by limitations of toxicity and efficacy, and the added difficulties of defining indications for safe and appropriate use.