Sorry for late reply. I do not actively check the .NET 3.5 updates now, so my list about these updates might be outdated. My computer have Windows XP and .NET 3.5 SP1, so anyone using .NET 3.0 (only) might get additional updates not mentioned below. Anyway, here's the list: (last update 2012-05-09) Updates | Patched component | Notes (All .NET 2.0 SP2 updates are needed for .NET 3.5 SP1) | ndp2.0sp2 | KB958481 (Download x86 x64 IA64) | ndp2.0sp2 | Note 1 KB958483 (Download x86 x64) | ndp3.0sp2 | Note 1 KB976769-v2 (Download) | ndp3.0sp2 | Note 2 KB977354 (Download) | ndp3.0sp2 | Note 3 KB2604110 (MS12-035, Download) | ndp3.0sp2 | KB2656407 (MS12-034, Download) | ndp3.0sp2 | KB958484 (Download x86 x64) | ndp3.5sp1 | Note 1 KB963707 (Download) | ndp3.5sp1 | KB2657424 (MS11-100, Download) | ndp3.5sp1 | KB2604111 (MS12-035, Download) | ndp3.5sp1 | Note 1: KB958481, KB958483, and KB958484 are offered to people who did a fresh install of .NET 3.5 SP1 . Those who updated from 3.5 to 3.5 SP1 (via KB951847) do not need these updates. These should be installed in this order: KB958481 -> KB958483 -> KB958484. Note 2: KB976769-v2 is contained in KB982168 so install KB982168 instead. (The rest of the KB982168 update is the same as KB982167 -- containing KB976765 and KB980773 which are both replaced) Note 3: KB982524 contains KB977354 but KB977354 may be downloaded separately. (The file name says NDP30SP2-KB977354-v2-x86.exe but the "v2" word does not appear in the update list after installation.) Update 2012-03-12 : Removed KB953595 - this hotfix is included in the .NET 3.5 installer. Update 2012-05-09 : May 2012 Patch Tuesday. Add KB2604110, KB2656407 and KB2604111.