METHODS: Fifteen (15) HIV-infected volunteers already being treated with a Crixivan and Norvir containing regimen will be recruited from the Grady Infectious Disease Clinic (IDP). Lexiva will be added to this regimen for 5 days, at the end of which participants will be admitted to the Grady General Clinical Research Center (GCRC) where blood samples will be collected at 9 different time points over 12 hours for measurement of blood drug levels.