Stand-by treatment is the use of anti-malaria drugs carried for self-administration when fever and flu-like symptoms occur and prompt medical attention is not available. This paper aims to review the rationale for the stand-by therapy concept, the range of options available, the factors influencing the choice of therapy and the efficacy and toxicity of the various agents available in the light of ever increasing resistance to conventional drugs. The use of chloroquine as a possible stand-by treatment is limited because of widespread chloroquine resistance and the problem is further compounded by the increasing prevalence of parasites resistant to antifolate/sulpha drug combinations, particularly in South-East Asia and South America. Mefloquine is a promising agent for presumptive malarial treatment with limited foci of drug resistance, notably in Thailand. Mefloquine therapy has been associated with adverse events, mostly minor but with occasional neuropsychiatric events. The use of halofantrine, hitherto often recommended as a stand-by treatment, has been curtailed after recent research reports demonstrated that the drug may cause prolongation of the QTc interval. Current experience with stand-by therapy is limited and studies are in progress to elucidate the exact circumstances under which travellers actually use their emergency medication. Stand-by treatment is an option for clearly defined situations while prophylaxis remains the safest choice for travellers to areas of high transmission.