To evaluate the safety and anti-Kaposi's sarcoma activity of ritonavir.

Inclusion Criteria

Concurrent Medication:

Allowed:

• Patients may receive oral acyclovir and may continue prophylactic treatment for PCP, fungal infection, MAC and toxoplasmosis.
• Topical treatment and intralesional chemotherapy will be allowed for lesions which will not be used as indicator or biopsy lesions.

Concurrent Treatment:

Allowed:

Localized radiotherapy will be allowed for lesions which will not be used as indicator or biopsy lesions.

Patients must have:

• Documentation of a positive ELISA test for HIV with a confirmatory test.
• Biopsy proven, cutaneous or oropharyngeal Kaposi's sarcoma.
• Vital signs, physical examination and laboratory assessments that exhibit no evidence of an acute illness.
• Patients must agree to report all current medications to the primary investigator and obtain prior permission to use them when feasible.

Exclusion Criteria

Co-existing Condition:

Patients with the following symptoms and conditions are excluded:

• Evidence of pulmonary Kaposi's sarcoma.
• Positive urine screen for recreational drugs.
• Current participation in another antiviral research study.
• Investigator anticipates poor patient compliance with the protocol.
• Patient has any condition that, in the investigator's opinion, may obscure the proper observation of the safety or activity of ritonavir.

Concurrent Medication:

Excluded:

• Antiretroviral therapy.
• Protease inhibitor therapy.
• Antiviral agent (e.g., oral ganciclovir or Foscarnet) or prophylactic medication for an AIDS defining illness which the patient cannot be removed from.
• Chemotherapy for Kaposi's sarcoma.
• Treatment with any medications that may interact with ritonavir.

Concurrent Treatment:

Excluded:

Radiotherapy for Kaposi's sarcoma.

Patients with any of the following prior conditions are excluded:

• History of psychiatric illness which is currently medically significant.
• History of pancreatitis.

Prior Medication:

Excluded:

• All antiretroviral therapy within 2 weeks prior to the start of the treatment phase of the study.
• Systemic chemotherapy of interferon within 30 days prior to study entry.
• Previous treatment with a protease inhibitor.

Risk Behavior:

Excluded:

Active substance abuse.