Pharsight does not officially support Phoenix products on Windows 8 at this time. However, we have just finished some preliminary testing with our Phoenix WinNonlin validation suite scripts and no issues have been found. The Phoenix WinNonlin 6.3 application appears to be stable on the Windows 8 platform. At this point no official support for Windows 8 is planned on our next release of Phoenix until this platform is more widely used. If you think that official support for Phoenix running on Windows 8 would be imperative to you in the near future, please send me an email at ana.henry@certara.com. Thanks Ana ana.henry@certara.com