After 33 years and 6,028 broadcasts of his late-night talk show, David Letterman is signing off.

The transplanted Hoosier, who made Top Ten lists and ironic humour staples of television comedy and influenced a generation of performers, is hosting his final episode of CBS' Late Show on Wednesday. Stephen Colbert will replace him in September.

Letterman announced his retirement last year and has kept details of his final show under wraps. The show tapes in late afternoon at Manhattan's Ed Sullivan Theater and airs at 11:35 p.m. ET.

Reporters weren't allowed inside the theater, but several audience members who filed out after the show had tears in their eyes.

"It was really incredible," said Will Landman of Long Island, N.Y. "It was the best way he could go out."

Audience members pointed to a star-studded Top Ten list and musical performance by the Foo Fighters as highlights.

David Letterman has called Foo Fighters his 'favourite band'. (consequenceofsound.com)

As for the host, Letterman "was guarded but you could tell it was really hard for him," said John Bernstein, who flew in from Los Angeles for the taping.

"You could see his emotion," he said. "But I think he's feeling a lot more than he's showing."

Anticipating the end

His last few weeks have been warmly nostalgic, with Letterman entertaining old friends like Bill Murray, Tom Hanks, George Clooney and Julia Roberts. Anticipating the end, viewers sent Letterman to the top of the late-night ratings the week before last for the first time since Jimmy Fallon took over at NBC's Tonight show and they competed with original telecasts.

From his start on NBC's Late Night in February 1982, Letterman's comedy was about more than telling jokes. He attached a camera to a monkey's back, tossed watermelons off a roof and wore a suit of Alka-Seltzer to plunge into a tank of water.

David Letterman sits at his desk on the television series 'Late Night with David Letterman,' in New York, 1986. (NBC Television/Getty Images) Celebrities used to being fawned over either clicked with his prickly personality or didn't, and when Cher called him a more profane version of "jerk," it became a memorable moment.

He shifted to CBS in 1993 when NBC gave the Tonight show to Jay Leno instead of Letterman, a slight he never forgot or forgave.

The tricks subsided as Letterman mellowed with age and fatherhood. His audience welcomed him back after a heart bypass, listened as he became the first late-night host back on the air after the 2001 terrorist attacks and saw him acknowledge to inappropriately having sex with a subordinate.

Future includes 'prostate health'

As retirement neared, Letterman joked about second thoughts. "Next week I'll be Googling foods that improve prostate health," the 68-year-old host said Tuesday. He also opened his heart: ending a segment with Oprah Winfrey last week, the microphone picked him up saying "I love you" as the two hugged. He shared a lingering last kiss onstage with Roberts.

Actor Bill Murray, left, talks with host David Letterman after emerging from a goodbye cake on Tuesday. ( John Paul Filo/CBS/The Associated Press) His penultimate show Tuesday could easily have been the last. Murray, his first guest on both the NBC and CBS shows, appeared after bursting out of a cake, smearing Letterman and those around him with icing.The Top Ten list was "Famous Last Words." Bob Dylan sang the standard The Night We Called it a Day.

Frequent foil Regis Philbin walked on, and they both expressed their admiration for each other. But not all of the famed Letterman edge had disappeared. He watched as Philbin slowly made his way up the aisle and out of the theater, shaking hands with audience members along the way.

"Take your time, Regis," Letterman deadpanned, falsely promising "we'll edit that right out."

He showed tape of several local CBS affiliate anchors discussing his retirement, misidentifying him as the Tonight show host. And he couldn't help but laugh as one anchorwoman said, "I do like him. It's hard to watch his show sometimes."

Rival Jimmy Kimmel paid tribute to Letterman by not making a fresh ABC show on Wednesday, where he usually competes in the same time slot. Fallon paid tribute on Tonight on Monday: "I, like every kid who grew up watching him, will miss him."