Does Bootcamp support 64 bit version of Windows 7? I have just purchased a Macbook Pro which will run OS X Lion. Which version of Windows can I run in Bootcamp? 64 or 32 bit? Both?
Version 4.0 of Bootcamp for Lion, released July 20, 2011, drops support for all versions of Windows XP and Vista.

It supports 32-bit or 64-bit Microsoft Windows 7 Home Premium, Professional, or Ultimate.

Boot Camp 4.0 FAQ from Apple Support.