Myron Cohen's cheeks have become sunken and his hands thin. He offers punch lines in a wispy murmur. He's 80 -- those Sunday nights on the Ed Sullivan show that made him a living-room star are two decades behind him -- so one logically cannot expect the same impish, jug-eared joker with the dialect-sprinkled spiel.

It's jarring, nonetheless, to hear his longtime manager caution against an interview that lasts longer than 15 minutes. It's sobering to learn that the blond woman at Cohen's side is the nurse who sees to his medication: Cohen had a serious heart attack a few years back and wears a pacemaker.

The Indigo Supper Club, a swank new room on the East Side, is filling with middle-aged couples who -- once the mike amplifies the weak voice -- will chuckle happily over the same routine Cohen has been reeling off for 40 years. For a hour a night, two hours on weekends, Cohen stands at the mike -- no stool, no water, no nurse, no breaks.

"The man doesn't blow a line," marvels the club's p.r. man, pausing in his glad-handing. "He remembers every story he ever told. He's unbelievable." Booked here for two weeks, his audiences bolstered by cronies from the Garment District and long-shuttered clubs, Cohen is outdrawing nearly all the club's previous acts, including comedians David Frye and Soupy Sales. Weekends, he sells out. A United Jewish Appeal benefit is bringing him, and singer Barbara Cook, to the Washington Hilton Sunday. Cohen also will entertain at the Hebrew Home in Rockville.

Waiting in the closet-like dressing room, Cohen, in a spotless dark suit and gold cuff links, drinks tea and smokes cigarettes while favoring a toe aching from a circulatory problem. Like a courteous great-grandfather, Cohen sits with his nurse and recounts his history.

He was a Garment District silkseller who had to ease past a buyer's sales resistance. "It was pretty well assumed that the next guy was selling the same goods," Cohen explains. "So I'd tell him a story. And he'd laugh. I'd tell him another story. He'd laugh. I'd forget what I came for. Ten minutes later, he's sold me a raffle book for the UJA.

"For instance, I tell a story about a little old Jewish man walking down Collins Avenue, very dejected because it's difficult to get a plane during the holidays. A friend spots him, says 'Where you living?' 'If I could get a flight, I'm living Thursday.' "

And how did a silk peddler turn, as Cohen says, to selling yarns?

"Long before you were born, darling," he begins, "there was a very famous club on 52nd Street called Leon & Eddie's Cafe." Sunday was Celebrity Night, when visiting comics--Berle, Hope, Buttons--would do a shtick and amateurs might grab a few minutes of attention. Cohen already was middle-aged--with his penchant for dialect, the emcee occasionally passed him off as a professor of languages at Columbia--but the audiences liked him. When Lou Walters ("Barbara's father, you know") hired him to play a club in Florida for a princely $1,250 a week, the rag trade lost its favorite jester.

"You're not gonna believe this," Cohen says, uncorking one of his bits. "Two partners are vacationing in the Catskill Mountains. One says, 'Morris, I'm hot like anything.' He goes for a swim; he gets a cramp. He yells, 'Morris, I'm drowning.' " And when Morris rescues him, pulls him back into shallow water and asks, exhausted, whether the partner can float alone now, what does the guy say? 'Morris, this is no time for talking business.' "

Cohen never knows which of these gentle anecdotes he'll retrieve for a performance. He doesn't try to give his trove of old jokes new kicks: The most recent cultural reference discernible in an hour-long set is to "one of those filthy Yippies."

That's okay with the crowd at the Indigo. When Myron Cohen takes the stage they will not be insulted, embarrassed or confused. "Tushy" is the raunchiest word they'll hear. In a Cohen story, when a woman at a bar tells an admirer she's a lesbian, the gentleman says, "So how's everything in Beirut?"

The nurse is looking at her wristwatch when a waiter knocks to announce visitors. Monroe Seton, the Celebrity Night emcee at Leon & Eddie's back when, is here celebrating his 43rd wedding anniversary with Muriel and wants to say hello. Cohen perks up. "We were in the same period," he explains, rubbing his hands together.

The talk is of old friends. "You know who was here last night? Joey Adams and Cindy!"

"Ahhh," says Seton, now white-haired.

"Jan Peerce had a stroke."

The Setons had not heard. They cluck.

"I lost my wife last year," Cohen goes on. Miriam had traveled with him to every fund-raiser and club date; his agent says Cohen wouldn't go around the corner without her. "Fifty-five years," Cohen quavers. He suddenly is weeping. His nurse tells the visitors to talk about something else. Cohen wipes his face with a handkerchief and the Setons are politely eased out.

"I've had better dressing rooms," Cohen says, recovering. "But as long as I have room to put my pants on . . . The important thing is out there. When I'm out there, I'm not thinking of anything but what I have to do to make people laugh. It hurts on the way home." His toe, he means.

He's never had an opening line other than, "I bid you a fond good evening, ladies and gentlemen," and he carefully walks, not bounds, toward the microphone. But he stands perfectly erect, and the spotlights help erase some of the hollowness from his face.

He starts unloading jokes at top speed, even jokes about his "little wife," in a Yiddish idiom to which the sound system lends body. Astonishingly, he becomes again the assured gagmeister of the Sullivan years.

"This was one of Ed Sullivan's favorite stories, God rest his beautiful soul," says Myron Cohen. "An Italian gentleman goes into a bank to borrow money and they tell him the loan arranger's out to lunch. 'Well,' he says, 'if the loan arranger's out to lunch, I'll talk to Tonto.'

"A gentleman in his eighties is watching television one night," continues Cohen. "His son stops by, says, 'What are you watching, Pop?' 'Basketball.' 'What's the score?' '86 to 82.' 'Who's winning?' '86.' "

The crowd is giggling contentedly. Cohen, announcing that this is a "beautiful audience," discharges another quarter-hour of jokes. Occasionally, someone calls out a favorite he wants retold. "Sahara!"

"Picture a skinny little guy, a shrimp, a nothing," Cohen obliges smoothly. "He walks into a lumber camp looking for a job." To impress a skeptical foreman, the shrimp fells a towering oak in 90 seconds. " 'Where'd you learn that?' says the lumberjack. The little guy says, 'In the Sahara Forest.' 'You mean the Sahara Desert.' 'Sure, now.' "

Who's left to reheat these chestnuts? George Jessel died last year. George Burns is still around, but he's doing commercials. Prime-time TV has no use for variety shows any more. Berle's doing off-Broadway drama. But Cohen's still wearing down the customers' resistance with stories in which the w's turn to v's.

"A little woman on her death bed summons her strength. 'You always were a wonderful husband,' she says. 'I want you should get married again right away. And all the fabulous gowns you gave me, the Christian Doors, the Balencikokkas, I want you to give her, she should look beautiful like I looked gorgeous.' The husband says, 'I could never do this.' 'Why not?' 'You're size 22; she's size 10.'"