AZT has been shown to delay the progression of AIDS in HIV infected individuals. However, bone marrow toxicity is a frequent adverse effect. Also, HIV resistance to AZT sometimes occurs in patients who initially respond to treatment, but later have progression of the disease. Thus, new drug treatments are needed. Studies of ddI in adults and children indicate some effectiveness of the drug. A direct comparison of AZT and ddI treatment in children has not been made. Combination antiviral treatment (AZT plus ddI) may give added therapeutic benefit to children.