The Safety and Effectiveness of Ritonavir in the Treatment of HIV-Related Kaposi's Sarcoma

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.