Background: Viral load in pediatric patients with HIV infections can help to make therapeutic decisions to modify the evolution of the disease. Aim: To evaluate viral load in positive HIV children with antiretroviral treatment. Material and methods: Viral load was measured every six months during three years in fifty pediatric patients chosen randomly in aged 1 to 12 years, using the Test Monitor HIV-1 AMPLICOR, versión 1.5. Results: During the three years follow up, there was an increase in CD4 and CD8 lymphocyte count and decrease in the viral load. However, there was no significant relationship between lymphocyte subpopulation counts and viral loads. Conclusions: Viral load demonstrated to be an appropriate method to quantify plasma HIV-RNA. This tool can help to define the condition of a particular patient to predict clinical course of the disease and to assess the response to the treatment.