Antiretroviral treatment will commence once patients meet the criteria for an initiation of the treatment as defined in the protocol. All antiretroviral agents that are currently approved by FDA for clinical indications in HIV-1-infected children (pediatric labeling) are permitted in the protocol. If the child has been receiving a single agent other than ddI, or has been on investigational antiretroviral agents, his/her antiretroviral therapy will have to be changed to an optimal combination regimen of the approved agents at least 6 weeks prior to the enrollment.