PIP: This paper presents facts on malaria epidemiology and historical perspectives of antimalarial drug use in Thailand. It also suggests that the use of an artesunate-mefloquine combination for treating falciparum malaria may be one of the factors responsible for the success of the country's control strategies. It is noted that in Thailand Plasmodium falciparum has evolved resistance to chloroquine, sulfadoxine-pyrimethamine, and mefloquine in succession. In view of this, administration of oral artesunate plus mefloquine became the standard treatment for microscopically confirmed uncomplicated falciparum malaria in 1995. The regimen requires administration of 300 mg/day of artesunate for 2 days plus 750 mg mefloquine on the first day, followed by 500 mg on the second day. Overall, it is too early to assume that the addition of artesunate has halted the progression of mefloquine resistance in Thailand. In terms of applicability of the regimen worldwide, the complexity of the factors involved makes it impossible to predict the useful lifespan of the artesunate-mefloquine combination on the Thai-Myanmar border. Further research is needed into the determination and validation of the most suitable antimalarial regimens for each epidemiologically distinct area and each operationally different circumstance.