Inclusion Criteria

Participant must be HIV-negative at entry and source must be HIV-positive. The source should be documented to be infected with HIV by one of the following criteria:

• Clinical diagnosis of AIDS or ARC.
• Positive test for HIV antibody (both ELISA and Western blot) or presence of HIV p24 antigen in serum.
• Participant may be enrolled if the source of exposure is suspected of being infected with HIV (member of risk group, some type of symptom of HIV infection), but the source must be confirmed to be infected with HIV for the participant to remain in the study.
• Significant exposure within 5 days prior to beginning therapy, defined as one of the following:
• Research laboratory workers or auxiliary personnel who, during the course of their work, were exposed to high titers of virus on abraded skin or mucous membranes or were accidentally inoculated with high titers of cell-associated or free virus through an exposed wound or puncture.
• Organ transplant recipients from HIV-positive donor.
• Recipients of blood or blood products from HIV-positive donor.
• Women who have been artificially inseminated with semen from HIV-positive donor.
• Other sources of exposure considered appropriate by the principal investigator and the sponsor.
• Persons with poor health (such as renal, hepatic, or bone marrow insufficiency) will be evaluated on a case-by-case basis.

Exclusion Criteria

Prior Medication:

Excluded within 4 weeks of study entry:

• Treatment with any potentially myelosuppressive drug.
• Nephrotoxic agents.
• Other experimental therapy.

Prior Treatment:

Excluded within 1 month of study entry:

• Blood transfusion with evidence of compromised blood marrow function.

Patients may not have any of the following:

• History of a malignancy other than cutaneous basal cell or cervical carcinomas.
• Significant, chronic underlying medical illness which, in the physician's judgment, would impair study completion.
• Liver dysfunction with bilirubin > 5 x ULN, alkaline phosphatase > 5 x upper limit of normal, or SGPT > 5 x upper limit of normal.
• Compromised bone marrow function with hemoglobin < 11 g/dl or blood transfusion within the last month, granulocytes < 1500 cells/mm3, or platelets < 100000/mm3.

When possible, no other concomitant medication will be administered during the treatment period.

Prior diagnosis of HIV infection by one of the following criteria:

• HIV antibody positive by ELISA or Western blot assays.
• HIV p24 antigen positive.
• Clinical symptoms which lead to a diagnosis by a licensed physician of AIDS / AIDS related complex (ARC) / AIDS dementia.

Active drug or alcohol abuse sufficient in the investigators' opinion to prevent compliance with the study regimen.