This issue of Clinics in Perinatology, guest edited by Drs. Athena Kourtis and Marc Bulterys, examines Perinatal HIV/AIDS. Authorities in the field have come together to offer reviews on topics including Epidemiology of perinatal HIV infection: US and worldwide; Biology of perinatal HIV transmission: Timing, virologic and immunologic factors; Viral sequencing from HIV-infected mothers and infants: Molecular evolution, diversity, and risk factors for mother-to-child transmission; Diagnosis of perinatally-acquired HIV infection; Prevention of mother-to-child transmission of HIV: Antiretroviral...