Malaria epidemiological surveys were carried out in two subdistricts; Meninting of Lombok island and Utan of Sumbawa island, Indonesia in 2002 through 2003. In Meninting, distribution of hypo-to meso-endemicity was observed mainly in hilly forested areas and partially in coastal areas with no distribution in the more densely populated flat areas surrounded by rice fields. In contrast, in Utan the distribution was limited to the coastal areas. In Utan, treatment follow-up studies revealed the prevalence of chloroquine resistant Plasmodium falciparum (P. f.). Although the degree of malaria endemicity in the two areas was regarded as hypo-to meso-endemic, the majority of affected individuals were under the age of ten, and the number of positive cases declined with increasing age. Interestingly, age dependence to species-specific infection was observed, younger children being more prone to P. vivax infections than to P. f.