Atazanavir (Reyataz) is a novel protease inhibitor (PI) approved for use in combination with other antiretroviral drugs for the treatment of HIV infection. In antiretroviral therapy (ART)-experienced patients the drug is administered with low-dose ritonavir (i.e. boosted). In the US, unboosted atazanavir is also approved for use in ART-naive patients. In adult patients with HIV infection, atazanavir-containing highly active antiretroviral therapy (HAART) regimens provided marked improvements in virological and immunological markers and was generally well tolerated. Furthermore, recommended atazanavir regimens were no less effective than, and generally as well tolerated as, other HAART regimens in these patients, including regimens containing co-formulated lopinavir/ritonavir. Atazanavir may have an advantage over other PIs because of its favourable effect on lipid profiles, once-daily dosing, low capsule burden and, in patients with low prior PI exposure, a favourable resistance profile. Given these advantages and taking into consideration between-country differences in the approved indications, atazanavir is a valuable option as the PI component of HAART for the management of HIV infection in adult ART-naive patients, particularly where metabolic complications are a concern, and as a first- or second-line PI in combination with low-dose ritonavir in adult ART-experienced patients.