The 2009 update to the list of drug resistance mutations (SDRMs) for surveillance of transmitted HIV-1 drug resistance includes 93 mutations, comprising 34 NRTI-associated mutations at 15 RT positions, 19 NNRTI-associated mutations at 10 RT positions, and 40 PI-associated mutations at 18 protease positions. This list was developed based on criteria that ensure mutations are non-polymorphic, occur at low frequencies, and are associated with drug resistance. The updated list includes 77 of the 80 mutations from the 2007 list, plus 16 new mutations, including four new NRTI-associated, three new NNRTI-associated, and nine new PI-associated mutations. These new mutations reflect changes in ARV use and resistance patterns, such as those associated with etravirine, tipranavir, and darunavir resistance. The list was created using publicly available sequences from ARV-naive individuals and includes mutations that are not polymorphic and occur at frequencies below 0.5% in most subtypes. The study emphasizes the importance of using a standardized SDRM list to compare transmitted resistance across regions and times, and to inform treatment guidelines. The list is not intended for individual patient management but rather for population-based surveillance. The study also highlights the challenges of distinguishing between true transmitted resistance and low-level polymorphisms, and the need for careful interpretation of surveillance data to avoid false positives. The updated SDRM list provides a valuable tool for monitoring HIV drug resistance and guiding public health interventions.The 2009 update to the list of drug resistance mutations (SDRMs) for surveillance of transmitted HIV-1 drug resistance includes 93 mutations, comprising 34 NRTI-associated mutations at 15 RT positions, 19 NNRTI-associated mutations at 10 RT positions, and 40 PI-associated mutations at 18 protease positions. This list was developed based on criteria that ensure mutations are non-polymorphic, occur at low frequencies, and are associated with drug resistance. The updated list includes 77 of the 80 mutations from the 2007 list, plus 16 new mutations, including four new NRTI-associated, three new NNRTI-associated, and nine new PI-associated mutations. These new mutations reflect changes in ARV use and resistance patterns, such as those associated with etravirine, tipranavir, and darunavir resistance. The list was created using publicly available sequences from ARV-naive individuals and includes mutations that are not polymorphic and occur at frequencies below 0.5% in most subtypes. The study emphasizes the importance of using a standardized SDRM list to compare transmitted resistance across regions and times, and to inform treatment guidelines. The list is not intended for individual patient management but rather for population-based surveillance. The study also highlights the challenges of distinguishing between true transmitted resistance and low-level polymorphisms, and the need for careful interpretation of surveillance data to avoid false positives. The updated SDRM list provides a valuable tool for monitoring HIV drug resistance and guiding public health interventions.