Parallels team, see report ID#28297321 if it gives you clues about the context. Parallels Desktop 9.0.23036 on Mac OS X Mavericks (all Developer Preview, up until the latest one DP7 10.9 13A569). Seen with a Windows 8 guest, but I doubt this is related to the guest kind. The full-screen option "Use Mac OS X full-screen" (free translation from my french UI "Utiliser le Plein Ã©cran de Mac OS X" does NOT work correctly (at all) on any display other than the primary display. On the primary display, it works fine : the full-screen VM integrates correctly as a Mac OS X full-screen app within Mission Control. On another display, the full-screen VM display and behaves as when the "Use Mac OX full-screen" is NOT checked. It does not display and behave like a Mac OS X full-screen app and Mission Control support is broken. In addition the Mac OS X menu bar stays visible at all times in such case. And weird resizing things happen on the secondary display, if I use Mission Control on the primary display to move to another full-screen app. The Windows guest reacts by resizing itself (when it should shave NOT reacted at all, not concerned). The very strange thing is that if in addition I check "stretch to all screens" (free translation from my UI "Etendre Ã tous les Ã©crans"), then the full-screen VM appears to use the Mac OS X full-screen mode (integrating quite well in Mission Control) on the secondary display. Though as this feature is meant to expose all screens to the VM (which is NOT what I want to do), there are additional strange issues occurring. The most disturbing one being that the VM thinks it has two displays, but whatever goes to the second display (seen by the VM) is NOT displayed anywhere. I understand these are wrong behaviors of PD 9 on OS X 10.9 Mavericks which is NOT yet released. But I understand too as a developer that Parallels Desktop teams have had the same time as any other developer to start taking Mavericks into account. As Parallels Desktop 9 and Mavericks have lived their beta period quite simultaneously, I would have expected Parallels to better support Mavericks before going to public release.