Dramatic advances in prevention and treatment of pediatric HIV infection occur in high-resource countries, but only 1% of the 2.3 million HIV-infected children live in these regions. Thus, two pediatric HIV epidemics have evolved, one in high-resource countries and one in low-resource countries. About the first epidemic, effective antiretroviral therapies for HIV in children have prolonged life and quality of life. As in adults, there has been evolution in causes of death over time, with decrease in AIDS-opportunistic infections and increase in 'end-stage AIDS' multiorgan failure, sepsis, and renal disease. In addition, spectrum of disease has changed: drug resistance (primary and acquired), lack of salvage drugs for children, complications of therapy, adherence, mental health, and adolescence-transition to adult care are the main problems that have emerged in the last years. In low-resource countries, few women know they are infected and there is poor access to antiretrovirals to prevent mother-to-child transmission, so children often present to health system with advanced disease and about 1000 infants are newly infected each day. Moreover, both diagnosis of infection in infants and drug access remain problematic: despite rapid progression and high mortality due to HIV in children, few receive treatment and, when available, it is started late. in this current evolving clinical context, we reviewed the epidemiology, clinical features, and treatment-related infectious complications of these two HIV-related epidemics. (C) 2008 Wolters Kluwer Health | Lippincott Williams & Wilkins