Carlin, who wrote on his Web site that he was "loaded on cocaine all week long" during his T.V. appearances in the late '70s and '80s, entered rehab in late 2004 for an addiction to alcohol and painkillers. The comedian had just finished a run headlining shows in Las Vegas.
In addition to a tour in 2006, Carlin filmed "Life Is Worth Losing" as an HBO special.
At left, Carlin bows as he opens the 13th annual U.S. Comedy Arts Festival at the Wheeler Opera House in Aspen, Colo., Feb. 28, 2007. (E Pablo Kosmicki/AP Photo)