Anti-HIV drug-resistant virus reverts to wild type following discontinuation of antiretroviral therapy (ART). This study aimed to determine the reversal period. ART was discontinued in 16 patients harboring drug-resistant viruses. Resistant mutations of reverse transcriptase (RT) and protease (PR) genes of plasma- and peripheral blood mononuclear cells (PBMC)-derived viruses were examined by direct sequencing monthly until the disappearance of mutants (median follow-up period: 8.9 months). Only wild-type virus was detected in 50% of patients at 6.3 months (quartiles, 3.2-20.7 months) and at 9.2 months (quartiles, 5.7-13.8 months) in plasma- and PBMC-derived viruses, respectively, after ART interruption. Among the 133 resistance-associated mutations identified at ART interruption, half the RT and PR mutations shifted to wild type in 3.2 months in plasma, 6.7 months of RT, and 5.7 months of PR in PBMC, respectively. In plasma- and PBMC-derived viruses, the PR mutations reverted earlier than the RT mutations. These results could be relevant as to when to perform drug-resistance testing.