A Multi-Center, Randomized, Double-Blind, Placebo-Controlled Study of the Efficacy and Safety of Adefovir Dipivoxil When Added to Standard Antiretroviral Therapy for the Treatment of HIV-Infected Patients With CD4 Cell Counts >= 200/mm3

Inclusion Criteria Patients must have: * HIV infection with HIV RNA titer \>= 2500 copies/ml (2.5 KEq/ml) plasma. * CD4 count \>= 200 cells/mm3. * No new AIDS-defining event within the past 2 months. * Life expectancy at least 1 year. * Consent of parent or guardian if less than 18 years old. * Tolerated antiretroviral therapy for the past 2 months. NOTE: * Kaposi's sarcoma is permitted provided patient has not received systemic therapy within the past month. Exclusion Criteria Co-existing Condition: Patients with the following symptoms or conditions are excluded: * Active, serious infections other than HIV that require parenteral antibiotic or antiviral therapy. * Gastrointestinal malabsorption syndrome or chronic nausea or vomiting that would preclude oral medication. * Malignancy other than Kaposi's sarcoma or basal cell carcinoma. Concurrent Medication: Excluded: * Immunomodulating agents such as systemic corticosteroids, IL-2, or interferons. * Isoniazid. * Rifampin. * Investigational agents (unless approved by sponsor). * Systemic chemotherapeutic agents. Prior Medication: Excluded: * Parenteral antibiotic or antiviral therapy for another active, serious infection within the past 2 weeks. * Immunomodulating agents such as systemic corticosteroids, IL-2, or interferons within the past month. * Systemic therapy for KS within the past month. Required: * Antiretroviral regimen other than study drug. Required: * Antiretroviral therapy for at least the past 2 months. Current alcohol or substance abuse that would interfere with compliance.