The development of HIV protease inhibitors led to renewed hope for an effective anti-AIDS treatment. But problems encountered in early studies of the new agents, such as hepatotoxicity, low oral bioavailability and insufficient potency, hampered the research efforts of several companies. However, perseverance has paid off, and a number of drugs with desirable properties are now undergoing extensive investigations. These include saquinavir, A-84538 and VX-478. At 2 recent conferences on antivirals [see main text for details], several speakers expressed their views on the current status of this class.