This December 2010 version of the International AIDS Society-USA (IAS-USA) drug resistance mutations list updates the figures last published in December 2009 (Johnson VA et al, Top HIV Med, 2009;17:138-145). This update includes 9 new mutations- E138G and E138K for etravirine (Haddad M et al, CROI, 2010; Abstract 574, and Vingerhoets J et al, Antivir Ther, 2010;15 [Suppl 2]:A125); E92Q for raltegravir (Geretti AM et al, Antivir Ther, 2010;15 [Suppl 2]:A62; Cooper et al, N Engl J Med, 2008;359:355-365; and Malet I et al, Antimicrob Agents Chemother, 2008;52:1351-1358); and M36L, M36V, H69R, L89I, L89M, and L89V for tipranavir/ritonavir. In addition, the tipranavir/ritonavir N83D mutation designation was changed to boldface to indicate its recognition as a major mutation rather than a minor mutation. The mutations I13V, K20M/R, E35G, and L90M were removed from the tipranavir/ritonavir bar, reflecting new understanding. For etravirine, L100I*, K101P*, and Y181C*/I*/V* are denoted with asterisks (instead of bolded) to reflect that these individual mutations each have the greatest impact (ie, highest weighting scores) on reduced phenotypic susceptibility and impaired clinical response when compared with other etravirine mutations (Haddad M et al, CROI, 2010; Abstract 574). In addition, user notes d, n, r, w, and z were revised.