Carlin says that he is entering treatment now before things get out of hand. "My levels of use are nowhere near the worst you hear about these days; I could easily have continued functioning at a good level ... for awhile. But my use would have progressed, I would have been in deeper trouble, and I didn't want to tolerate that." 

In the 80s, the 67-year-old comedian also battled cocaine addiction but reportedly quit on his own. 

It is not known at press time how long Carlin will be in rehab. He reported entered a treatment center on Monday. He is scheduled to appear at the Stardust Hotel in Las Vegas in February.