The HIV reverse transcriptase and protease sequence database (HIVRT&PrDB) is an online relational database that catalogs evolutionary and drug-related sequence variations in the HIV reverse transcriptase (RT) and protease enzymes, which are molecular targets of antiretroviral therapy. The database includes nearly all published HIV RT and protease sequences, along with data on the source of the sequences, the antiretroviral drug treatment history of the individuals from whom the sequences were obtained, and results of in vitro drug susceptibility testing. It also plans to add sequences and data on two new molecular targets of HIV drug therapy—gp41 (cell fusion) and integrase—by 2003. The database is designed to assist scientists in designing new HIV-1 drugs, clinical investigators in studying drug resistance, and clinicians in using genotypic HIV-1 drug resistance tests. It contains data from over 420 published papers, sequences from more than 7000 individuals, and about 20,000 drug susceptibility results from tests on over 2000 virus isolates. The database allows users to retrieve sequences meeting specific criteria and provides sequence interpretation programs for comparing new sequences with published ones and inferring drug resistance levels.The HIV reverse transcriptase and protease sequence database (HIVRT&PrDB) is an online relational database that catalogs evolutionary and drug-related sequence variations in the HIV reverse transcriptase (RT) and protease enzymes, which are molecular targets of antiretroviral therapy. The database includes nearly all published HIV RT and protease sequences, along with data on the source of the sequences, the antiretroviral drug treatment history of the individuals from whom the sequences were obtained, and results of in vitro drug susceptibility testing. It also plans to add sequences and data on two new molecular targets of HIV drug therapy—gp41 (cell fusion) and integrase—by 2003. The database is designed to assist scientists in designing new HIV-1 drugs, clinical investigators in studying drug resistance, and clinicians in using genotypic HIV-1 drug resistance tests. It contains data from over 420 published papers, sequences from more than 7000 individuals, and about 20,000 drug susceptibility results from tests on over 2000 virus isolates. The database allows users to retrieve sequences meeting specific criteria and provides sequence interpretation programs for comparing new sequences with published ones and inferring drug resistance levels.