David Letterman has learned the Power of Oprah: her "Late Show" appearance Thursday earned him his biggest audience in more than a decade.

An estimated 13.5 million people stayed up late to watch Winfrey's first visit to Letterman in 16 years, Nielsen Media Research said on Friday. Only three times has Letterman had a bigger audience on CBS — for his network premiere in 1993 and twice in 1994 in the midst of the Nancy Kerrigan- Tonya Harding ice skating melodrama.

Winfrey's appearance more than tripled Letterman's typical audience of 4.3 million viewers, Nielsen said.

Letterman escorted Winfrey to the nearby Broadway premiere of "The Color Purple" after their chat. Winfrey co-produced the musical, at least partly explaining the timing of her Letterman appearance.

During the interview, Winfrey said she thought Letterman's infamous 1995 joke on the Academy Awards ("Oprah, Uma. Uma, Oprah") was funny — although she did pointedly present him with a signed portrait of herself with Uma Thurman.

"I have never for a moment had a feud with you," she said.

The summit between the talk titans was set up by years of Letterman jokes about Winfrey, mixed in with years of her rejecting offers to appear on the show, and endless promotion promotion since her visit was announced.

The "Late Show" audience was larger than that of most prime-time programs and appeared to consist almost entirely of people who usually don't watch late-night TV. Incredibly, Jay Leno on NBC's "Tonight" show was seen by 6.2 million people on Thursday — more than his season average of 5.8 million — evidence that Leno's usual fans didn't abandon him.

"Late Late Show" host Craig Ferguson basked in Letterman's glow. His show, which directly follows Letterman, had its biggest audience ever early Friday, Nielsen said.