Inclusion Criteria

Concurrent Medication:

Allowed:

• Chemoprophylaxis for Pneumocystis carinii pneumonia, candidiasis, Mycobacterium tuberculosis, and herpes as prescribed by the investigator.
• Recombinant erythropoietin and G-CSF if clinically indicated.

Patients must have:

• Documented HIV infection.
• CD4 count 300 - 500 cells/mm3.
• Prior AZT therapy for at least 3 months but less than 12 months prior to study entry.
• No past or current AIDS-defining opportunistic infection.

Exclusion Criteria

Co-existing Condition:

Patients with the following symptoms or conditions are excluded:

• Kaposi's sarcoma requiring systemic therapy.
• Active malignancy other than basal cell carcinoma or in situ cervical carcinoma.

Concurrent Medication:

Excluded:

• Antiretroviral therapy other than AZT.
• Immunosuppressive drugs.
• Investigational HIV drugs/therapies other than study drug.
• Interferon.
• Steroids.
• Hematopoietins.
• Cytotoxic chemotherapy including Adriamycin, bleomycin, and vincristine.

Concurrent Treatment:

Excluded:

• Radiation therapy.

Patients with the following prior condition are excluded:

History of treatment-limiting intolerance to 500-600 mg AZT daily as manifested by the same recurrent grade 3 toxicity or any prior grade 4 toxicity.

Prior Medication:

Excluded:

• Prior antiretroviral therapy other than AZT.

Required:

• AZT for at least 3 months but no more than 12 months prior to study entry.