The role of STIs in the transmission dynamics of HIV epidemics is paradoxical and complex. Population-based studies have found that both the prevalence and incidence of HIV were substantially higher among people with STIs. However, randomized trials have found STI treatment to have little to no effect on HIV incidence. Even though STI treatment does not seem to have a significant impact on HIV incidence, effective management of STIs is an essential public health activity, especially for improved maternal and child health outcomes. Data linking the prevalence of STIs with increased risk of HIV transmission and acquisition underscore the importance of STI prevention, which can best be achieved through a comprehensive STI control program.