Plasmodium falciparum malaria and HIV are among the most important infectious diseases in sub-Saharan Africa. Approximately two-thirds of the estimated 35 million HIV infected persons live in sub-Saharan Africa. Of the 300-500 million annual cases of malaria infection occurring worldwide, about 90% of P. falciparum infections occur in sub-Saharan Africa, resulting in approximately 1 million deaths, mostly in children under five years of age. It is clear that HIV and malaria are responsible for substantial disease, suffering, and an enormous economic burden on the people who can least afford it. Although a study in 1993 in Tanzania showed significantly higher prevalence of malaria infections in HIV-positive compared to HIV negative adults, until recently there have been few studies showing any association between the two infections.