The conservative commentator exited last Wednesday from what he called "five intense weeks" of treatment for his addiction.
He told listeners that his ordeal would not affect his radio program. He said there was more about his experience that he wanted to tell but could not.
"I've not been phony here," he said. "I've not been artificial on the program. I was all of that elsewhere. I was all that other places, but not here. And all of this will reveal itself."
Limbaugh had not appeared on the air since Oct. 10, before going into a rehabilitation program in Arizona.
Limbaugh had said he started taking prescription painkillers when a doctor prescribed them following spinal surgery. Back pain stemming from the surgery persisted, Limbaugh said, so he kept taking pills and became hooked.
A law enforcement source in Palm Beach County, where Limbaugh owns a $24 million oceanfront mansion, said last week that Limbaugh's drug use is still under investigation by the state attorney's office.
In the past, Limbaugh had decried drug use and abuse on his bluntly conservative show, arguing that drug crimes deserve punishment.
On his broadcast Monday, Limbaugh denied he was guilty of any hypocrisy in his attitudes toward drug crimes.
"I was a drug addict from about 1996, 1995 or whatever, to just five weeks ago," he said. "The truth of the matter is I avoided the subject of drugs on this program for the precise reason that I was keeping a secret."
He called the experience of rehabilitation probably the most educational five weeks about himself that he had ever spent.
"I have to admit that I am powerless over this addiction that I have," he said. "I used to think I could beat it with force of will. I used to think that I would be different, but I'm not."
He profusely thanked his audience for standing by him and said he came to realize how important his program was to him.
Limbaugh, whose show reaches some 600 markets and about 20 million listeners a week, was broadcasting from a studio in Manhattan. The industry trade publication Talkers magazine predicted his audience was probably about three times its normal size for his return.
"He's slightly reinvented," said Michael Harrison, publisher of Talkers. "He's the same basic Rush that people have come to know very well, with a new element to it as an unknown that increases his value as a radio property."
Harrison said he was struck, in listening to Limbaugh's return, at how important the show seemed to him.
"With his will and his talent, that indicates he's going to be around for a long time," he said.
He remains a polarizing figure. A new Gallup poll conducted earlier this month found that 34 percent of Americans hold a favorable review of Limbaugh, while 51 percent view him unfavorably. The poll of 1,004 adults, conducted Nov. 10-12, found 35 percent of conservatives now have a negative view of Limbaugh.
Limbaugh gave up his job as an ESPN sports analyst Oct. 1, three days after saying on the sports network's "Sunday NFL Countdown" that Philadelphia Eagles quarterback Donovan McNabb was overrated because the media wanted to see a black quarterback succeed. The drug allegations surfaced around the same time.
Since Limbaugh left the show, his spot has been filled by several guest hosts, including Tony Snow, Walter Williams and Matt Drudge.
Much of Limbaugh's bluster returned intact on Monday.
"I know the sky probably seems brighter to you no matter where you are," he said. "The air is cleaner, the water is purer, and it's not because of the environmentalist wackos. It's because I'm back, right?"
And after talking about his rehab, Limbaugh turned to a familiar subject -- attacking Massachusetts Democratic U.S. Sen. Edward Kennedy.