1. In order to help interpret the antiviral activity of indinavir, the virologic and immunologic profile of children will be studied within 2 weeks prior to starting the therapeutic part. For children who have never been treated, this will be before the initiation of any antiretroviral therapy and for children who have already received antiretroviral therapy, this will be done during the initial "wash-out" phase that is routinely interposed between two different treatment regimens.