Problems with installing the rgl package on Linux

Dear All,

I am trying to install the rgl package on R 2.6.1 running on Fedora 8
(Linux), but I am experiencing the following problems:

-----------------------------------------
configure: error: X11 not found but required, configure aborted.
ERROR: configuration failed for package 'rgl'
** Removing '/usr/lib/R/library/rgl'
-----------------------------------------

Any ideas?

Thanks in advance,

Paul