A Phase III, Randomized, Double-Blind, Multicentre Study to Evaluate the Safety and Efficacy of 1592U89 in Patients With AIDS Dementia Complex

Inclusion Criteria Patients must have: * Documented HIV infection. * Evidence of HIV - associated dementia. * Been on stable antiretroviral treatment for a minimum of 6 weeks prior to study entry. Exclusion Criteria Co-existing Condition: Patients with any of the following symptoms or conditions are excluded: * Debilitated as a result of their HIV disease, associated illness or therapies who the investigator determines will not be able to complete the 12 week randomized dosing period. * Memorial Sloan-Kettering (MSK) score of \>= 3 for dementia. * Confounding neurological diseases which may interfere with interpretation of neurological and neurophysical assessments. * Malabsorption syndrome or other gastrointestinal dysfunction which renders them unable to take oral medication. * Chronic diseases such as diabetes, congestive heart failure, cardiomyopathy, other cardiac dysfunctions, etc., which in the investigator's opinion would compromise the safety of the patient. * Symptomatic AIDS-defining opportunistic infection not responsive to therapy. Concurrent Medication: Excluded: * Treatment with cytotoxic chemotherapeutic agents within the first 12 weeks of the study. * Treatment with nerve growth factor within the first 12 weeks of study. * The use of narcotic analgesics, sedatives, benzodiazepines, antidepressants, anti-psychotic agents and other psychoactive drugs which would interfere with the assessment of the neurological and neurophysical status of the patient. * Use of stavudine (d4T) during the first 12 weeks of the study. * Immunomodulating agents (except GM/G-CSF or epoietin). * Psychoactive drugs (at the investigator's discretion). Concurrent Treatment: Excluded: * Treatment with radiation therapy within the first 12 weeks of the study. NOTE: * With the exception of local treatment for Kaposi's sarcoma. Patients with any of the following prior conditions are excluded: * Previous neurological disease unrelated to HIV infection. * History of clinically apparent hepatitis within the last 6 months. * History of clinically apparent pancreatitis in the last 6 months. Prior Medication: Excluded: * Treatment with cytotoxic chemotherapeutic agents within 1 month of entry. * Participation in investigational antiretroviral trials within the past 3 months. * HIV vaccine within the past 3 months. * Treatment with immunomodulating agents such as systemic corticosteroids, interleukins, thalidomide, anticytokine agents, anti-oxidants or interferons within 1 month of study entry. * Nerve growth factor. Prior Treatment: Excluded: * Treatment with radiation therapy within 1 month of entry. NOTE: * With the exception of local treatment for Kaposi's sarcoma. Risk Behavior: Excluded: Current alcohol or illicit drug use which may interfere with the patient's ability to comply with the study protocol. Required: * Stable antiretroviral treatment that has been ongoing for a minimum of 6 weeks prior to study entry, may or may not include ZDV. Required: * Stable antiretroviral treatment for a minimum of 6 weeks prior to study entry.