Inclusion Criteria

Concurrent Medication:

Allowed:

   - Chemoprophylaxis against Pneumocystis carinii pneumonia (PCP), Mycobacterium
   tuberculosis, or Herpes simplex virus, or against other opportunistic infections as
   indicated.

   - Corticosteroids for no longer than 21 days (only as part of PCP therapy).

   - Erythropoietin and G-CSF.

Patients must have:

   - Documented HIV-seropositivity.

   - CD4 count 100 - 300 cells/mm3.

   - Prior continuous AZT dose = or > 300 mg/day for 1 year or longer.

Prior Medication: Required:

   - AZT for at least 1 year prior to study entry.

Exclusion Criteria

Co-existing Condition:

Patients with the following symptoms and conditions are excluded:

   - Medical contraindication or is considered noncompliant in the opinion of the
   investigator.

   - Peripheral neuropathy = or > grade 2.

Concurrent Medication:

Excluded:

   - Anti-HIV agents other than study drugs.

   - Biologic response modifiers (other than erythropoietin or G-CSF).

   - Systemic cytotoxic chemotherapy.

   - Regularly prescribed medications (such as antipyretics, analgesics, allergy
   medications) that are associated with an increased risk of pancreatitis, peripheral
   neuropathy, or bone marrow suppression.

Concurrent Treatment:

Excluded:

   - Radiation therapy.

Patients with the following prior conditions are excluded:

   - History of acute or chronic pancreatitis, gout, or uric acid nephropathy.

Prior Medication:

Excluded:

   - Other antiretrovirals besides AZT.

   - ddI or ddC for more than 30 days within the past year or any time within 3 months
   prior to study entry.

   - Acute therapy for an infection or other medical illness within 14 days prior to study
   entry.