Abstract: The migratory labor system in South Africa draws large numbers of men away from rural areas and often places them in single sex hostels, prompting contacts with sex workers and the HIV-infection of their partners. As inadequate information exists on HIV/AIDS and internal migration�s relationship, this study examines the quantitative impact of migrants� risky sexual behavior on HIV/AIDS prevalence of provinces. We found that an increase in the magnitude of risky sexual behavior of in-migrants, poor in-migrants and out-migrants results in an increase in HIV/AIDS prevalence, while that of non-poor in-migrants results in its decrease. We also found that the distances between the provinces of origin and destination matter in the spread of HIV/AIDS. The estimates indicate that HIV/AIDS prevalence in a province increases more with the increase in out-migration than that in in-migration or is more responsive to the former than to the latter. Therefore, we suggest some policy interventions to reduce the spread of HIV/AIDS related to South African internal migration.