Our study will examine the influence of race and sex on the 24-hr pharmacokinetics of lopinavir/ritonavir (an antiretroviral agent commonly used in naïve patients) following a switch from LPV/r 400/100 mg twice daily to 800/200 mg once daily dosing. Tolerability (measured by toxicity grade of diarrhea) and change in quality of life following switch from twice daily to once daily dosing will also be assessed using appropriate validated measurement tools.