Enfuvirtide [T 20, 'Fuzeon'] is the first drug in a new class of antiretroviral agents known as HIV-1 fusion inhibitors. The addition of enfuvirtide to an optimised background regimen in treatment-experienced patients with HIV-1 infections has been found in two large pivotal phase III trials to significantly decrease plasma viral load and significantly increase CD4+ cell count at 24 weeks. However, enfuvirtide is a costly drug and works best in conjunction with other active drugs, thus its cost effectiveness is a salient issue in the HIV infections treatment arena. In addition, as enfuvirtide requires twice-daily injections, and often causes painful injection-site reactions which persist throughout therapy, its impact on patients' health-related QOL (HRQOL) is of great interest to physicians and patients alike. These issues were examined in studies which were presented at poster sessions during the 2nd International AIDS Society Conference on HIV Pathogenesis and Treatment [Paris, France; July 2003].