Inclusion Criteria

Patients must have:

• HIV infection.

Prior Medication: Included:

• Patients in Part 1 must have received no previous zidovudine (AZT) or a stable dose of at least 500 mg/day without evidence of toxicity.
• Patients in Part 2 must have received no previous AZT or = or > 300 mg/day for < 6 consecutive weeks within 1 year prior to study entry.

Exclusion Criteria

Co-existing Condition:

Patients with the following conditions or symptoms are excluded:

• Acute HIV-related opportunistic infection requiring ongoing treatment.
• Diarrhea defined as 3 or more liquid stools/day for one week.
• Wilson's or Gilbert's disease, porphyria, or other chronic or acute hepatic disease.
• Potentially life-threatening allergic reactions to any of the components of zidovudine.
• Acute or chronic medical conditions that in the opinion of the investigator would place patient at risk by participation in this study.

Concurrent Medication:

Excluded:

• Systemic bronchodilators, acetaminophen, aspirin.

Prior Medication:

Excluded:

• Didanosine (ddI) or dideoxycytidine (ddC) within 14 days prior to entry.
• Immune modulators or investigational drugs within 30 days prior to entry.
• Drugs known to induce hepatocellular enzymes, such as phenobarbital, phenytoin, warfarin, ketoconazole, and oral contraceptives, within 30 days prior to entry.

Patients in Part 2 only:

Excluded:

• Zidovudine within 4 weeks prior to receiving first dose of study drug.

Risk Behavior:

Excluded:

• Patients who the investigator feels would not comply with study requirements.

Patients may not have the following prior conditions:

• Acute or chronic medical conditions that in the opinion of the investigator would place patient at risk by participation in this study.
• Potentially life-threatening allergic reactions to any of the components of zidovudine.