Apple will release OS X Mountain Lion in July for $19.99. The specification requirements for running OS X Mountain Lion is similar to OS Lion. If you’re running OS X Lion, your Mac is compatible and upgradable to OS X Mountain Lion. If you’re running OS X Snow Leopard or earlier version of OS X, please note the requirements as Mountain Lion does not run on older Macs.
Apple has published an OS X Mountain Lion technical specification page where it details the requirements. Supported Macs include iMac (mid 2007 or newer), MacBook (late 2008 aluminum or early 2009 or newer), MacBook Pro (mid/late 2007 or newer), MacBook Air (late 2008 or newer), Mac mini (early 2009 or newer), Mac Pro (early 2008 or newer) and Xserve (early 2009).
OS X Mountain Lion will only be available via Mac App Store, and requires minimum OS X Snow Leopard 10.6.8 or later, 2G memory and 8GB of free disk space.