LOS ANGELES — When Craig Ferguson took over CBS' "The Late Late Show" a year ago, the fledgling host said the program (weeknights, 11:30 p.m.) would be a work in progress — but he didn't say that would be the case every night.

Since then, an improvised style has emerged, with monologues that forsake scripts and live comedy bits that favor unpredictability over precision.

For an actor (Mr. Wick on "The Drew Carey Show") with no previous hosting experience, the 43-year-old Scot sounds comfortable with the gig he took over from Craig Kilborn.

"It's what I do now," Ferguson says, after mapping out that evening's monologue, a riff on "King Kong." "The most relaxing hour of the day for me is doing the show. It's like a warm bath."

Audiences have been responding. "The Late Late Show" is averaging 1.9 million viewers since the fall TV season started, a 9 percent increase over last year. Although Ferguson trails NBC's Conan O'Brien, he has set ratings records for the CBS show in the past three Nielsen sweeps months, when local stations set ad rates.

Ferguson may be an accidental host, but executive producer Peter Lassally, who worked closely with Johnny Carson and David Letterman, says he saw the potential after just a handful of tryout shows in the fall of 2004.

"I felt he could get through to an audience. He has an enthusiasm and humor that just breaks through the screen," Lassally says.

And "he's a great storyteller," chimes in co-executive producer Gary Considine.

The latter skill wasn't well served by the late-night tradition of scripted monologue jokes. Ferguson first tried that approach, with lackluster results. But it was the host's spontaneous commentary after the death of Carson that foreshadowed his eventual style.

Last April, Ferguson told Lassally he wanted to dump the scripted jokes and his tie. "Peter said, 'I can't tell you how delighted I am' " about the monologue, Ferguson says. "And he said, 'No way are you wearing a tie.' " The host has since discarded both.

Ferguson has a similar approach in the show's comedy segments. He conducts most of his impersonation bits — his repertoire includes Michael Caine and Sean Connery — live and improvised. He'll also answer viewer e-mail that he sees for the first time on air or decide to write a letter to David Letterman, pulling out a quill pen and composing on the spot.

When it doesn't quite work, there's the impish grin or the Scottish burr. Women love Ferguson's accent and have helped boost what had been Kilborn's frat-house audience. The accent also lets him get away with double-entendres that seem naughty rather than tasteless.

The guest list looks different, too, under the new host. Ferguson has stuck to a plan to bring on a diversity of guests, such as writers, a rare commodity in celebrity-heavy late night. Guests have included authors and a Harvard anthropologist who explained how some tribes survived the Asian tsunami.

On show days now, Ferguson talks with the show's writers about what has happened to him or what interests him. They'll pick a topic, discuss some ideas and stories he can relate and then map it out in bullet points. There's no script.

"He will digress. That makes it fun," Considine says.

But it can cause headaches, too, when a monologue designed for 11 minutes runs for 14.

Ferguson's "King Kong" monologue started with the movie ape, veered into the economics of crack, ranted about movie-ticket prices and somehow got into cloning. He says that kind of digression keeps the monologue from getting stale. "If I don't know what's going to happen next, then the audience can't, either."