A Randomized, Double-Blind, Three-Arm Study Comparing Combination to Monthly Alternating Nucleoside Therapy for the Treatment of Advanced HIV Disease (CD4 <= 50/mm3) With a Prior History of Nucleoside Therapy

Inclusion Criteria Concurrent Medication: Required: * PCP prophylaxis. Allowed: * Erythropoietin. * Prophylaxis for MAI or fungal infections. * Antibiotics. * Over-the-counter, alternative, or regularly prescribed drugs. * Steroids, if for \< 21 days. Concurrent Treatment: Allowed: * Radiation therapy for cutaneous Kaposi's sarcoma. Patients must have: * HIV infection. * CD4 count \<= 50 cells/mm3. * Prior nucleoside monotherapy for at least 6 months. * Life expectancy of at least 6 months. Prior Medication: Required: * Nucleoside monotherapy for at least 6 months. Active alcohol or drug abuse. Exclusion Criteria Co-existing Condition: Patients with the following symptoms or conditions are excluded: * Severe peripheral neuropathy. * Psychological or emotional problems sufficient to prevent study compliance. Concurrent Medication: Excluded: * Systemic chemotherapy for malignancy. * Acute or induction therapy for opportunistic infection. Patients with the following prior conditions are excluded: * History of acute or chronic pancreatitis. * Grade 3 or greater toxicity to AZT, ddI, or ddC on two or more occasions. Prior Medication: Excluded: * Non-study nucleosides or biologic response modifiers within 7 days prior to study entry. * Acute therapy for opportunistic process within 14 days prior to study entry. * Acute systemic therapy for other medical conditions within 14 days prior to study entry.