The purpose of this study was to compare the safety, tolerability, and antiviral activity of once-daily (QD) and twice-daily (BID) dosing of the lopinavir/ritonavir (LPV/r) tablet formulation in combination with nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) in antiretroviral-experienced human immunodeficiency virus type 1 infected subjects with detectable viral load while receiving their current antiretroviral therapy.

Inclusion Criteria:

• Subjects were human immunodeficiency virus type 1 (HIV-1) positive, antiretroviral-experienced adults at least 18 years of age currently receiving an antiretroviral regimen which had not changed for at least 12 weeks.
• Subjects had plasma HIV-1 ribonucleic acid (RNA) levels > 1,000 copies/mL at screening and were not acutely ill.
• Subject was currently failing his/her antiretroviral regimen with the most recent 2 consecutive prestudy plasma HIV-1 RNA levels > 400 copies/mL with the most recent being > 1000 copies/mL, and in the investigator's opinion, should change therapy
• Female subjects were nonpregnant and nonlactating.

Exclusion Criteria:

• Subjects were excluded if screening laboratory analyses showed hemoglobin <= 8.0 grams per deciliter.
• Subjects were excluded if screening laboratory analyses showed absolute neutrophil count <= 750 cells/microliter.
• Subjects were excluded if screening laboratory analyses showed platelet count <= 50,000 per cubic millimeter.
• Subjects were excluded if screening laboratory analyses showed alanine aminotransferase (ALT) or aspartate aminotransferase (AST) >= 5.0 x upper limit of normal (ULN).