Jon Stewart takes over as the host of Comedy Central's 'Daily Show tomorrow night, but don't expect many changes in the nightly news parody. ''Except I'll be reading the news with a Yiddish accent,'' Mr. Stewart warned, and proceeded to ad-lib the day's headlines sounding uncannily like Jackie Mason. ''We're going after the audience that never got over the cancellation of Chicken Soup,'' he said, referring to the Jackie Mason-Lynn Redgrave sitcom that made a brief and forgettable appearance in 1989.

But seriously, what changes does the stand-up comedian foresee for the show, which has established a loyal following over the past two years? During an interview in the TriBeCa offices of Busboy Productions, his Miramax-based production company, Mr. Stewart, 36, professed not to know where the show was headed. ''I'm going into this thinking that it's a great show, I have a pretty strong comic voice, and we're going to spend the first three months trying to blend those two things. It's not rocket science.''

The show's original host, Craig Kilborn, a former ESPN announcer, left last month to take over Tom Snyder's Late Late Show on CBS. Mr. Kilborn blended boyish charm with a sardonic attitude that perfectly reflected the show's viewpoint. Mr. Stewart, who is handsomer in person than in his photos, which often exploit his willingness to look goofy for the camera, declined to compare his style to his predecessor's, other than to note that he is significantly shorter than 6-foot-4 Kilborn. ''They're getting rid of the tallest people on the show so that I don't look ridiculous,'' he added.

Madeleine Smithberg, the show's executive producer, pointed out that the two men are ''polar opposites.'' ''Craig likes to gaze in the mirror,'' she said. ''Jon doesn't own a mirror. Craig tends to appeal to frat boys, Jon to rock-and-rollers.''

In fact, the studio audience at taping of the show last month was composed almost entirely of college-age men, making it raucously clear that after two years the still show runs very smoothly. ''Every day the world deals us a hand,'' Ms. Smithberg said. ''And we've built a machine that can cope with it.''

On that ''machine,'' an opening ''Headlines'' segment intersperses actual news footage with wry commentary from the host, and on-location segments feature reports from the show's ''correspondents.'' Then there is ''The Five Questions,'' a regular feature in which a celebrity guest is interviewed by the host and then asked such toughies as ''Goobers or Raisinets?''; this is in many respects Mr. Kilborn's signature segment, and may follow him to CBS, though it's owned by Comedy Central.

'The Daily Show With Jon Stewart (as it is now called) is taped in Manhattan four days a week (Monday through Thursday) at 6:30 P.M. for broadcast that night at 11, so the pressure to produce something that is both timely and funny is intense. ''It's a writer-driven show,'' Mr. Stewart noted. ''The fuel is really topical, and I'm accustomed to writing jokes quickly. On paper it will be the exact same show as before. On paper Letterman and Leno are the exact same show. But there will be a different atmosphere.''

The Daily Show won't be Mr. Stewart's first regular television job. He had a recurring role as the fictitious guest host on the final season of The Larry Sanders Show and was the host of his own late-night talk show, first on MTV and later in national syndication, from 1993 to 1995. He's also appearing in two movies : The Faculty, directed by Robert Rodriguez, and Playing by Heart (opening later this month) with Gillian Anderson and Sean Connery.

But comedy, not acting or writing, will remain his focus. ''I still don't have the actor's vocabulary down,'' he said. ''Interviewers always ask me to describe my character in a film, and all I can say is, 'Well, he's my height.' ''

Mr. Stewart hopes the show's satiric take on the news will encourage people to lighten up. ''Impeachment? Y2K? Look, my fear is whether we'll survive so many Dateline's and 20/20's.'' You watch those shows and you'd think we were falling apart: 'You won't believe what's in that cheeseburger!' 'Did you know that your airbag could decapitate you?' ''

''Oddly enough,'' he added, ''The Daily Show is one of the most responsible news organizations because we're not pretending to be news in the first place. Our one rule is, no faking.''