Chrome was released almost exactly a year ago, and is currently available in 32-bit versions for Windows, Linux and Mac OS X.
However, 64-bit on the desktop is much more commonplace in the Linux world, and Google is likely to be responding to pressure from Linux users for a 64-bit release.
The move was revealed in a developer forum posting by Google Chrome software engineer Dean McNamee, along with a link to build instructions for those interested in trying out the 64-bit code.
The 64-bit version under development is actually a port of Chromium, the open-source code on which the release version for Windows is based.
Google said that the V8 JavaScript engine at the core of Chrome does not currently compile in 64-bit mode on Windows. Development efforts are focused on making the 64-bit version of V8 work on Linux and Mac first, but Windows support is coming.