A seroepidemiologic survey of Plasmodium vivax and Plasmodium falciparum transmission was conducted in 94 Orang Asli children and adults. The prevalence of malaria was 46% in this population, and infections due to P. vivax and P. falciparum occurred with equal frequency. Multi-species infection was common, particularly in children <10 years of age. Circumsporozoite (CS) antibodies to P. vivax were detected by ELISA, using the recombinant protein NS181 V20, in sera from 53–95% of all subjects in this study. The specificity of reactivity to NS181 V20 was confirmed by immunofluorescence using air-dried sporozoites. CS antibodies to P. falciparum were present in <50% of the population <30 years of age. These data support further testing of this protein as a candidate vivax vaccine.