Recommendations for the prevention of malaria among travelers have been developed by CDC in consultation with representatives from the Offices of Medical Services of the Department of State and the Peace Corps; the Division of Experimental Therapeutics of the Walter Reed Army Institute of Research; the Office of the Surgeon General, U.S. Army; the Office of the Surgeon General, U.S. Air Force; and the Bureau of Medicine and Surgery, U.S. Navy. Resistance of Plasmodium falciparum to chloroquine has spread to most areas with malaria. Alternative drugs to chloroquine are either associated with adverse reactions, are of limited efficacy, or require complex and detailed instructions for use that reduce compliance. These factors have contributed to a threefold increase in the number of reported P. falciparum infections among U.S. travelers to malarious areas since 1980. A new drug, mefloquine (Lariam), is expected to be highly effective against both chloroquine-resistant and Fansidar-resistant P. falciparum infections. Mefloquine is now recommended as the drug of choice for travelers at risk of infection with chloroquine-resistant P. falciparum. Alternative drugs for travelers who cannot take mefloquine include 1) doxycycline alone or 2) chloroquine alone, with Fansidar available for standby treatment while medical care is sought for evaluation of febrile illness when travelers are in a malarious area. Prospective travelers and health-care providers are advised to call the CDC Malaria Hotline at (404) 332-4555 for detailed recommendations for the prevention of malaria.