Let me say that I look very handsome behind that desk." notes Chevy Chase as he watches himself on a giant TV screen. "I'm sure I could handle Carson's job for, oh, 10 or 15 years."

Of course he's kidding. But let's face it: Chevy Chase thinks he's hot stuff, and right now he is - he helped save the Oscar show, made the cover of Esquire, got profiled in TV Guide and, tonight, stars in his first network prime-time special.

"The Chevy Chase show" will be seen at 10 on Channel 4 and other NBC stations.

Chase is no longer a Not Ready for Prime Time Player on NBC's "Saturday Night. " He is in fact ready, and the first graduate of that program to get his own prime-time showcase. Big deal, Orson Welles made "Citizen Kane" when he was 25. Chase is 33. And "The Chevy Chase Show" is not nearly as good as "Citizen Kane." It is quite good however - with one or two buts.

"The Chevy Chase Show" is by turns funny, very funny, not very funny, acrobatic, irreverent, bright, flip, shamelessly violent, slightly refreshing, at times too cute and largely lacking human warmth. Just like Chevy Chase in person.

Dor Chase, in person, does not seem especially likeable. There is something precious and preppy about him. But it's this very obnovious part of his personality that makes him so much fun to watch and sometimes fascinating; he's almost as irresistible in his smugness as Jack Paar was in his emotionalism. They are blood brothers of the tube. On a Friday afternoon, Chase sits with fellow writer Tom Leopold, assorted friends, a six-pack of Michelob and a baggie filled full of oranges, doing the final audio mix for the show at a Hollywood sound studio. Chase and an engineer called Al sit behind the console full of controls and watch the show played back on an oversized TV screen in front of them.

Chase has been working on the show for two months. This is the last technical step before it is finished. Much of the canned laughter that was on the cound track is taken out by Chase at this point, to cheers from Leopold. He also decides to remove an "Ugh!" he had made when shocked in the head by a car door.

With his array of gizmos, Leopold can summon up various elements of the soundtrack on different isolated channels to take out Chase's groan, but he must play and replay portions of the videotape until he finds the portion of the channel with the groan on it.That means we get to see Chase konked on the noggin over and over again.

There is some pleasure in watching this, and Chase seems to share it.

The show is filled with physical comedy, which is not a surprise from Chase, who traditionally began each "Saturday Night" with an elaborate topple. On the special, Chase is attacked by a golfer, hung from a hook like a butchered cow, blown up at a gas station and run over by a car that is driven by his actress wife, Jacqueline.

At the editing session, Chase effortlessly catches orange slices behind his back, tosses beer bottles into a distant waste basket (once nearly beaning a reporter) and flips a lighted cigarette into his mouth, pretending to swallow it. Chevy Chase is like the teen-age goof-off who never grew up. A friend says he will pretend to fall out of his car at Stop lights in order to get laughs on the street.

Sort of pathetic, isn't it? But there's something compulsively funny about Chase and his compulsion to be funny. And the special, which also features Tim Conway and an odd grab-bag of guests, takes sly satiric aim at a number of pomposities, most of them of the type inflicted by television. Perhaps only Chevy Chase would undertake and carry off a spoof of the Emergency Broadcast System tests.

The most audacious sketch stars Jack La Lanne as himself with a program of exercises for the dead. "Just because you passed away is no reason to go to pieces" says Jack.

Chase doesn't laugh much as he watches the playback of the show. But when Conway appears under a mountainous hairpiece as the host of a doggie disco show. Chase laughs so hard he has to stand up and circle his chair once.

He also goes to pieces over the show's theme song, which he plays on a small cassette recorder. It's "Mary Had a Little Lamb" made to sound just like the theme of "The Tonight Show Starring Johnny Carson."

"We even used Carson's back-up drummer," says Chase as he plays the tap. "I love it. It's something to have. It's just on the edge of getting us sued."

There's been a lttle tension between Carson and Chase since last year, when the rumor started that NBC was grooming Chase as the next Carson. Chase denied it. Carson, in an interview at his home last summer, made a derisive and virtually unprintable remark about Chase's ability to ad lib. Chase barked back from New York, "I'll go one on one adlibbing with him anytime."

It was one of the great feudes. But it appears to be over. Lanky, whacky Chase was scheduled to be a guest on the Carson show last night to plug the special, according to an old NBC tradition. Chase and Carson met for the first time Tuesday and Chase said later that everything about the meeting was cordial.

Back at the sound studio, Chase is oblivious to the fact that while he works on his special, two of his friends are pantomining erotic acts behind him. After nearly eight hours of audio editing. Chase runs the special all the way through for himself and his manager, executive producer Marty Erlichman. During blank spaces where commercials will be inserted, Chase says things like, "Well, it moves right along. If you hate one thing, it's over pretty quick. Then he adds with mock dismay, "Oh, it'll never get on anyway."

Chase insists that the special is not the pilot for a series. His NBC contract calls for one special a year for three years. "The series option is entirely mine," he says, "and I'm not going to take it now." No, hell, I don't want to do a series." Instead he'll writing a movie script with Michael O'Donoghue, former National Lampoon editor and now the writer responsible for the sickest humor on "Saturday Night." Chase says he still watches "Saturday Night" everytime its' on.

He is scheduled to speak tonight to students and faculty at Harvard Law School. Why, of all people, him? "They could have anybody they wanted and they wanted me," says Chase, with his little-boy defiance. He says he'll "try" to finish his speech in time to watch himself on television. Try? That's a good one. He wouldn't miss a minute of it for the world.