Fglrx

AMD Catalyst (previous fglrx: FireGL and Radeon for X ) is the proprietary graphics driver for AMD/ATI graphic cards. The open source alternative is radeon.

Kernel
You need to activate the following kernel options:

Driver
The actual package name for the driver is.

Note the USE flags of :

Initial setup
This will generate an initial xorg.conf which uses the fglrx driver:

If this command fails without error, copy the file to the default location:

Set the OpenGL driver to use fglrx:

Settings
The most comfortable way for most users is to use as a graphical UI to configure the driver.

External resources

 * Community Gentoo Wiki article
 * X.Org Wiki