The purpose of this study is to assess two regimens in antiretroviral-naive subjects.

The purpose of this study is to assess two regimens in antiretroviral-naive subjects.

• Drug: Viread (tenofovir disoproxil fumarate )
• Drug: Emtriva (emtricitabine)
• Drug: Combivir (zidovudine + lamivudine)
• Drug: Sustiva (efavirenz)

Inclusion Criteria: Subjects must meet all inclusion criteria within 28 days prior to randomization unless specified otherwise:

• Plasma HIV-1 RNA levels greater than 10,000 copies/mL using Roche Amplicor HIV-1 Monitor Test Version 1.5 Standard
• Adequate renal function: Calculated creatinine clearance greater than or equal to 50 mL/min according to Cockcroft-Gault Formula.
• Hepatic transaminases (AST and ALT) less than or equal to 3 x upper limit of normal (ULN).
• Total bilirubin less than or equal to 1.5 mg/dL.
• Adequate hematologic function (absolute neutrophil count greater than or equal to 1,000/mm3; platelets greater than or equal to 50,000/mm3; hemoglobin greater than or equal to 8.0 g/dL).
• Serum amylase less than or equal to 1.5 x ULN.
• Serum phosphorus greater than or equal to 2.2 mg/dL.
• Willingness to use effective contraception by both males and females while on study treatment and for 30 days following study drug completion.
• Life expectancy greater than or equal to 1 year
• The ability to understand and sign written informed consent form obtained prior to initiation of study procedures.

Exclusion Criteria: Subjects are not eligible for study if any of the following are met:

• Prior treatment with any non-nucleoside reverse transcriptase inhibitor (NNRTI), nucleoside reverse transcriptase inhibitor (NRTI), or protease inhibitor (PI).
• A new AIDS-defining condition diagnosed (exception CD4 criteria) within 30 days of baseline.
• Receiving ongoing therapy with any of the following: nephrotoxic agents, probenecid, systemic chemotherapeutic agents, systemic corticosteroids, interleukin-2, drugs that interact with efavirenz. Administration of any of the above medications must be discontinued at least 30 days prior to baseline visit and for duration of study.
• Pregnant or lactating subjects.
• Malignancy other than cutaneous Kaposi's sarcoma (KS) or basal cell carcinoma. Subjects with biopsy confirmed KS are eligible but must not have received any systemic therapy for KS within 30 days of baseline and not anticipate starting systemic therapy during the study.
• Prior history of renal or bone disease.
• Any other clinical condition prior to therapy that would make the subject unsuitable for the study or unable to comply with the dosing requirements in the opinion of the investigator.