The current version of ClamXav is compatible with Tiger.

With older versions of the ClamAV engine, some people reported that the ClamAV user (which is required for the updating of virus definitions) appears at Tiger's login window. Please note that this problem was fixed in a subsequent ClamAV Engine Installer and is no longer an issue. Update to the newest version of the ClamAV engine to sort the problem.

If you are running Mac OS X Server 10.4 Tiger, DO NOT attempt to install the ClamAV Engine.