Ultra-deep sequencing (UDS) is a powerful tool for exploring the impact on virological outcome of minority variants with low frequencies, some even ,1% of the virus population. Here, we compared HIV-1 minority variants at baseline, through plasma RNA and PBMC DNA analyses, and the dominant variants at the virological failure (VF) point, to evaluate the impact of minority drug-resistant variants (MDRVs) on virological outcomes. Methods: Single-molecule real-time sequencing (SMRTS) was performed on baseline RNA and DNA. The Stanford HIV-1 drug resistance database was used for the identification and evaluation of drug resistanceassociated mutations (DRAMs). Results: We classified 50 patients into virological success (VS) and VF groups. We found that the rates of reverse transcriptase inhibitor (RTI) DRAMs determined by SMRTS did not differ significantly within or between groups, whether based on RNA or DNA analyses. There was no significant difference in the level of resistance to specific drugs between groups, in either DNA or RNA analyses, except for the DNA-based analysis of lamivudine, for which there was a trend towards a higher prevalence of intermediate/high-level resistance in the VF group. The RNA MDRVs corresponded to DNA MDRVs, except for M100I and Y188H. Sequencing from DNA appeared to be more sensitive than from RNA to detect MDRVs. Conclusions: Detection of pretreatment minority HIV-1 RTI-resistant variants by UDS showed that MDRVs at baseline were not significantly associated with virological outcome. However, HIV-1 DNA sequencing by UDS was useful for detecting pretreatment drug resistance mutations in patients, potentially affecting virological responses, suggesting a potential clinical relevance for ultra-deep DNA sequencing.