Comparison of Stavudine Used Alone or in Combination With Didanosine in HIV-Infected Children

Inclusion Criteria Patients must: * Be on-study, on-treatment in ACTG 240, or receiving AZT monotherapy by prescription for at least 6 months immediately preceding enrollment. * Have laboratory evidence of HIV-1 infection \< 18 months - 2 positive viral tests \>= 18 months - 2 positive viral tests or 2 or more positive tests for HIV antibody * Have parent or legal guardian willing to sign a consent. Prior Medication: Required: * On-study, on-treatment in ACTG 240 (D4T or AZT) or receiving AZT monotherapy by prescription for at least six months immediately preceding this trial. Exclusion Criteria Co-existing Condition: Patients with any of the following symptoms or conditions are excluded: * Intractable diarrhea or vomiting. * Current clinical or laboratory Grade 3 or worse toxicities. Concurrent Medication: Excluded: * Concurrent use of antiretroviral agents other than those provided by the study, immunomodulators (other than IVIG or corticosteroids), or other investigational drugs except for those in ACTG 254 and ACTG 219. * Chemotherapy for active malignancy. Patients with any of the following prior conditions are excluded: * Reached an ACTG 240 defined endpoint, or are permanently off ACTG 240 study treatment. * Prescription AZT recipients may not have received \> 6 weeks of d4T or ddI previously. * Subjects who have had chemotherapy for active malignancy. Prior Medication: Excluded: * Prescription AZT recipients may not have received \> 6 weeks of d4T or ddI previously.