RT sequences of 1083 HIV-1 strains obtained from the HIV complete sequence database (http://www.hiv.lanl.gov/content/ sequence/NEWALIGN/align.html) were aligned and compared. Based on the X-ray crystal structures of HIV-1 RT (1RTH) from the Research Collaboratory for Structural Bioinformatics Protein Data Bank (RCSB PDB), structural models of wild type and mutant RTs were analyzed using Swiss-PdbViewer software (http://spdbv.vital-it.ch/).