As you may have heard, Apple has released to its Developer Community a preview of the next version of OS X: OS X Mavericks. What is the easiest way to use a new operating system, especially a early preview of an operating system currently still under development? In a virtual machine in Parallels Desktop, of course. So, the Engineering team at Parallels has released Knowledge Base articles about installing OS X Mavericks in Parallels Desktop 8 and about installing Parallels Desktop 8 on a Mac that is running OS X Mavericks:
The company notes that users cannot install Mavericks into a clean virtual machine, but they can upgrade an already existing OS X virtual machine to Mavericks with only a few minor changes.