Objective To evaluate the reproducibility of an in-house HIV-1 drug resistance(HIVDR) genotyping test.Methods The reproducibility of an in-house HIVDR genotyping test was evaluated with 204 plasma samples,which had been tested from 2008 to 2010.The samples were randomly selected and retested with the same method.A fragment of HIV pol gene was extracted from plasma samples,amplified and sequenced.Drug resistance-related mutations were identified and interpreted through Stanford HIVdb program,and were compared with the results of previous testing.Results The rates of concordance in the overall resistance and resistance to specific antiretroviral drugs were 98.5%(201/204)and 92.2 %(188/204) between the results of the first and second testing,respectively.One hundred and sixty-seven(81.9%)specimens had same levels of resistance to specific antiretroviral drugs between the two sets of results.However,the discordant drug resistance-related mutations were found in 84 samples,among which 159 discordant codons were discovered.Most(149) of the codons were partially discordant.The inconsistent codons were most frequently found at position 71(13/204,6.4%) of the protease and 103(12/204,5.9%) of the reverse transcriptase(RT), respectively.Ten completely discordant codons were found at position 71 of the protease.Nucleoside reverse transcriptase inhibitor(NRTI) resistance-related sites were found at position 67,69,70,215 and 219 and non-nucleoside reverse transcriptase inhibitor(NNRTI) resistance-related sites were found at position 90,181 and 221 of RT regions,respectively.Conclusions The results revealed high concordance rates in both the incidence and the degree of drug resistance.The reproducibility of the in-house drug genotyping test procedure can be optimized by further standardization and personnel training.