Until recently, treatment for human immunodeficiency virus type 1 (HIV-1) infection was limited to the use of nucleoside inhibitors of the viral enzyme reverse transcriptase. While these agents initially offered promise, they have only modest antiviral activity and the benefits of treatment are limited by the emergence of drug resistance and dose-limiting toxic effects. 1,2 Development of more potent drugs that target different stages of the virus life cycle has thus been aggressively pursued. Efforts to develop inhibitors of HIV-1 protease have yielded a potent new class of compounds that suppress HIV-1 replication to an extent far greater than was previously attainable. Four protease inhibitors, saquinavir mesylate, ritonavir, nelfinavir, and indinavir sulfate, have been approved by the Food and Drug Administration. Other agents are undergoing active investigation. The purpose of this article is to review the currently available data on those agents that have been approved for clinical use. Arch Intern Med. 1997;157:951-959