A malaria prevalence study was performed in a village in Irian Jaya, Indonesia, that contains a population of people who have been exposed lifelong to hyperendemic malaria and another population of people who had arrived 18 months previously from areas of very low endemicity. Mean spleen sizes correlated positively with prevalence of malaria, not resistance to it. Prevalence of sexual and asexual blood stage parasites was higher in transmigrants than in the natives. The data also show that clinical resistance to malaria in this part of the world includes resistance to Plasmodium falciparum gametocytemia and that this is not the passive byproduct of a reduction in asexual parasites. This indicates that the introduction of native people into a populated malarious area will increase the percent of gametocyte carriers and may, thereby, increase the entomologic inoculation rate.