sempron ~ # emerge -p --depclean

*** WARNING ***  Depclean may break link level dependencies.  Thus, it is
*** WARNING ***  recommended to use a tool such as `revdep-rebuild` (from
*** WARNING ***  app-portage/gentoolkit) in order to detect such breakage.
*** WARNING ***
*** WARNING ***  Also study the list of packages to be cleaned for any obvious
*** WARNING ***  mistakes. Packages that are part of the world set will always
*** WARNING ***  be kept.  They can be manually added to this set with
*** WARNING ***  `emerge --noreplace <atom>`.
*** WARNING ***
*** WARNING ***  As a safety measure, depclean will not remove any packages
*** WARNING ***  unless *all* required dependencies have been resolved.  As a
*** WARNING ***  consequence, it is often necessary to run
*** WARNING ***  `emerge --update --deep world` prior to depclean.

Calculating dependencies... done!

Dependencies could not be completely resolved due to
the following required packages not being installed:

~kde-base/kde-env-3 required by kde-base/kdelibs-3.5.2-r6

Have you forgotten to run `emerge --update --deep world` prior to depclean?

sempron ~ #