show Abstracthide AbstractLow-frequency variants containing non-nucleoside reverse transcriptase inhibitor (NNRTI) resistance mutations were associated with virologic failure in patients receiving first-line cART (Li et al., 2011). In addition, using allele-specific PCR, Rowley et al. demonstrated that low-frequency variants containing K103N and Y181C increased the risk of treatment failure of nevirapine (Rowley et al., 2010). Next generation sequencing, due to its relatively long sequencing read length, can efficiently detect mutations in the context of a sequence and not just a single locus (Fisher et al., 2012). One of the approaches is ultra-deep pyrosequencing (UDPS) which sequences millions of PCR amplicons, such as sequencing on the Roche 454 platform. However, few studies have been conducted to evaluate the usefulness of UDPS in the detection of low-frequency DR variants in clinical settings (Fisher et al., 2012; Johnson et al., 2008; Li and Kuritzkes, 2013; Li et al., 2011).Therefore, the aim of this study is to characterize the DR of HIV-1 CRF07_BC isolates using different assays including UDPS.