Atazanavir (formerly BMS-232632), an azapeptide protease inhibitor (PI), is a new human immunodeficiency virus (HIV) treatment that has recently received marketing approval from the FDA. It has a pharmacokinetic profile that supports once-daily dosing and has demonstrated a unique resistance profile and superior virologic potency compared with other antiretrovirals in vitro. In subjects with HIV, atazanavir (400 mg once daily) produced rapid and sustained improvements in viral load and CD4 counts in both antiretroviral-naive as well as previously treated patients when used in combination with dual nucleoside reverse transcriptase inhibitor (NRTI) treatment. In these studies atazanavir demonstrated comparable anti-HIV efficacy to nelfinavir (twice or three times daily), efavirenz and the combination of ritonavir and saquinavir. However, unlike these comparator agents, atazanavir did not adversely affect the plasma lipid profile, an advantage that sets it apart from other currently available PIs. Atazanavir was inferior to lopinavir/ritonavir in patients who previously failed an initial protease inhibitor containing regimen. Preliminary results in multiple PI-experienced patients indicate comparable efficacy to lopinavir/ritonavir in subjects receiving a boosted regimen of atazanavir plus ritonavir. In summary, atazanavir offers several therapeutic advantages, including a convenient once-daily dosing schedule, neutral lipid effects and a distinct resistance profile. These characteristics may ultimately help improve adherence, reduce the potential risk of long-term cardiovascular events associated with dyslipidemia, and increase the range of therapeutic options available for patients failing other antiretroviral regimens.