Microsatellite markers derived from simple sequence repeats have been useful in studying a number of human pathogens, including the human malaria parasite Plasmodium falciparum. Genetic markers for P. vivax would likewise help elucidate the genetics and population characteristics of this other important human malaria parasite. We have identified a locus in a P. vivax telomeric clone that contains simple sequence repeats. Primers were designed to amplify this region using a two-step semi-nested polymerase chain reaction protocol. The primers did not amplify template obtained from non-infected individuals, nor DNA from primates infected with the other human malaria parasites (P. ovale, P. malariae, or P. falciparum). The marker was polymorphic in P. vivax-infected field isolates obtained from Papua New Guinea, Indonesia and Guyana. This microsatellite marker may be useful in genetic and epidemiologic studies of P. vivax malaria.