Two important problems for patients with HIV infections receiving highly active antiretroviral therapy (HAART) are its potential to elevate cholesterol and triglyceride levels, and the development of resistance to one or more agents in their treatment regimen. Studies presented at the 10th Conference on Retroviruses and Opportunistic Infections [Boston, US; February 2003] suggest that treatment with the investigational protease inhibitor (PI) atazanavir has advantages over established PIs with respect to these concerns. Results from an open-label study indicated that atazanavir has durable efficacy, with responses maintained after 108 weeks' treatment in patients receiving the drug in addition to lamivudine and stavudine. Furthermore, switching to atazanavir was shown to improve serum lipid profiles in patients previously treated with nelfinavir, while improving virological response rates. In an analysis of data from several studies, atazanavir was shown to have a unique resistance profile, with researchers suggesting that early use of, and development of resistance to, the drug does not affect − and may in fact enhance − susceptibility to other PIs in later treatment regimens.