AIDS: Researchers convened in Italy to discuss state-of-the-art antiretroviral treatment, the most recent data on the development of resistance in naive and experienced patients, and ways to reconstruct the immune system in the early and later stages of HIV disease. Participants reviewed data on a new generation of genotypic and phenotypic assays that portend a new model of care for guiding treatment decision-making in the face of treatment failure. Several papers described new mechanisms of resistance for nucleoside, nucleotide, nonucleotide reverse transcriptase inhibitors, and protease inhibitors. Other studies reported on the evolution of drug resistance, the problem of transmission of drug-resistant viruses, and the potency of regimen adjustments. Discussions revealed the need for academia and industry to continue to develop novel antiretroviral agents.