In Hanoi, a Vietnamese surgeon lined up about 15 of his patients, and tried to explain their illness to visiting American surgeon LaSalle Leffall Jr. through an English interpreter. The translations were fizzling until Leffall suggested the doctors speak in French. Then they communicated.

In Argentina, the health groups put a picture of Leffall, president of the American Cancer Society and chairman of the surgery department at Howard University, in a full-page newspaper ad. That visibility landed him on national television discussing "Roots."

LaSalle Leffall's adaptability as both the public, almost celebrity, physician, and as the private doctor and cancer surgeon, has made him one of the better-known medical names in the country.

Leffall's 48-year course from Quincy, Fla., to chateau-charmed work trips has been marked by a drive to come out first, to accomplish goals quickly and a hesitancy to make waves. He entered Florida A and M University at age 15, finished in three years, and graduated from Howard University Medical School at age 22 with one of the best academic records ever. In the last 18 years he has helped build up the medical school, putting, says his predecessor, "Howard's surgery department on the map." The praise of his surgical colleagues is unanimous. "His reputation is such that I consider him a superior surgeon," says John F. Potter, director of Georgetown's Lombardi Cancer Center.

Surgeons enjoy a certain glory, like jet pilots or nuclear physicists. They are at once caretakers of humanity, but expected to be humanly faultless, priests and strokers.

Consummate becomes an understatement applied to Leffall's dedication to medicine. He arrives at the hospital at 4:45 a.m. each morning, refuses to let anyone else take his students and puts socializing down the list, once missing most of a garden party at the British Embassy to console Marvella Bayh.

And as president of the world's largest volunteer health agency, Leffall moves in a highly charged atmosphere that is politicized by the many people vying for American Cancer Society support -- and for the cancer society's help in directing the many millions the federal government spends for cancer research and prevention.

Leffall includes a black perspective in his myriad dealings, however, keynoting with obvious pride the first national conference on cancer and black Americans, which is meeting through today at the Capitol Hilton Hotel.

Leffall's piercing, stentorian voice can be heard around the corridors at Howard Hospital. He's an unmistakable figure, tall and broad like one of his heroes, Muhammad Ali, with a handsome smile that breaks frequently over a boxy face. A dedicated lover of jazz, languages and tennis Leffall pulsates with life.

"He doesn't waste a second. He squeezes everything that life has to give. The main thing is that he is a humanist, he goes beyond the doctor's duties," says Marvella Bayh, a cancer patient and activist with the American Cancer Society.

His friends call him "The Swinger." Lately Perrier has replaced the Cokes. But he has never been pious, joining his Alpha fraternity brothers in writing Greek symbols on packages of black-eyed peas, hanging out with his close friend, the late Julian Cannonball Adderley, and enjoying evenings of best-sellers, forbidden chocolates and Charlie Parker.

On occasions the two personas converge. At his installation dinner as ACS president at the Waldorf-Astoria Hotel last November, he quoted Teilhard de Chardin on the energies of love.

Afterwards a group of friends insisted they test the waters at Studio 54, the den of the chic and the freaked. Leffall danced the hustle, sipped soft drinks and marveled at the glittery goings-on. As they left, a member of the party complained about a lump in her throat and Leffall examined her under the street light. A few days later, as he was writing thank-you notes, he read about the IRS raid at Studio 54 and called his friend, columnist Carl Rowan, laughing, but totally conscius of his public image. "That's all I would have needed was to have been picked up in a drug bust."

In the rarified world where surgeons live, the burden of the patient's desire for infallibility is always there, a miracle on the human machinery. His own self-esteem is more vital than an ordinary professional; he has to be confident to the point of arrogant, quick to make a decision, spare of outward emotions.

"You can't let yourself think you are omnipresent, things can go wrong, things you don't have control over. Medicine and surgery are very humbling," says Leffall. His brown-rimmed bifocals reflect the X-ray light on his office wall, giving the coffee skin a burnished look. The walls of the small, unpretentious office at the hospital are lined with medical degrees, books, and plaques. A television set looks out of place. As the discussion changes gears several times, Leffall pulls himself straight in the chair, takes an audible deep breath and rapidly charges each issue.

On this rarified pedestal, the position of the black surgeon, nearly as rare as black symphonic conductors, is even more striking. Not until Charles Drew, who later discovered a blood plasma preservation method, began his specialized training in the late 1930s were blacks encouraged to choose surgery. Hospitals were segregated, blocking training outside four black institutions. White patients sometimes refused to let a black touch them. Changes were slow. Leffall, and many of his contemporaries, only occasionally saw the inside of a white institution until they finished their residence. But Leffall last year was offered the chief-of-surgery position at Memorial Sloan-Kettering Cancer Center in New York, one of the world's most prestigious, but turned it down because of the ACS demands.

Whenever he goes on a long trip, Leffall misses the exercise, the drama and fulfillment of the operating room. "After I had been in China a month, I was extremely anxious to get back. Over the years you achieve the ability to react properly, to determine how to pay attention to each detail," says Leffall. The ultimate achievement, he says, using a slogan students and colleagues attribute to him, is equanimity under duress.

The talk of particular operations, the best and the worst, seemed to make Leffall uncomfortable. He sighs, he squirms. "The worst time is when you think you are going to find something favorable, a cancer localized, and it has spread," says Leffall, quickly, almost impatiently. "The best feeling is when you think you will find the worst. When all the signs point to advanced cancer and it isn't."

At the end of each day, Leffall has his private moment of reflection. "I discuss with myself, what did I do that I shouldn't have done, what didn't I do that I should have done."

He gets up, wanks down the hall to a lab where, along with another doctor, he is doing research on cancer of the large intestine and rectum. "What I would like to do now with 28 years of training and growing is make some original contribution in surgery." The words of a complete physican.

In the LaSalle Leffall lore there's the essential fable about him healing a bird as a youngster. His sister, Delores Leffall, a librarian at Anacostia High School, tells it proudly.

In Leffall's memory there's little doubt that the motivation toward medicine was the foresight and persistence of his parents.

"My folks, particularly my father, said that he and my mother as teachers were doing something imparting knowledge but a physician could do so much more," says Leffall. His father, a school principal, was the only one of 11 siblings to go to college, and stressed education as the highest value. "He would say education can take you through; your mother and I can't leave you anything."

The idea of knowledge, the fact that you could memorize Longfellow's Maud Miller and the bones of the skull and it would stay with you forever, Leffall found exciting.

Florida A and M, known for its marching band and defensive backs, made Leffall, the scholar and the sixth player on the basketball traveling team, a hero.

Even now Leonard Spearman, a ranking official at HEW, chuckles over their antics. "We used to borrow the dean of women's car, on the pretense of washing it. And use up all her gas driving our girlfriends around," says Spearman. "And with all those smarts one time he got us lost. The frat brothers led us into the woods, blindfolded and we had to get back. Leffall led us around a swamp, filled with alligators, 10 miles in the wrong direction."

In college, the heroes of his youth, Joe Louis and Paul Robeson, were supplemented by author Frank Yerby, a successful novelist. "I choose people to admire because they stand up for a cause, excell in what they did, or showed general concern," says Leffall. "I read all of Yerby's books and liked the way he describes things."

Howard, where he entered medical school in 1948, provided different role models, the black physicians who had been stung, but not stymied by racism, and who had wordly views. Leffall heard W. Montague Cobb speak of wisdom, received inspired incentive from Charles Drew and confidence from Burke Syphax and Jack White. Medicine became his world.

While a senior at Howard, Leffall met Ruth McWilliams, then a recent education graduate of Virginia Union College, on her way to New York. "It seems to me we were introduced near the emergency room. My sister was engaged to a resident. I never made it to New York," says Ruth Leffall. "He was clean-cut, nice, intelligent, exceedingly kind to people. He seemed interested in his work."

The year after the Leffalls married, he went to Memorial Sloan-Kettering Cancer Center in New York, the second black to have a senior fellowship there.

When Capt. Leffall returned from one year in the Army in Germany he joined the staff at Howard and the local chapter of the ACS. Some of the other black doctors who were active left because of what they perceived as tokenism and insensitivity to minority issues and cancer. "When I had disagreements in the local, years ago, it was over policy, some discussions being made without full consultation," says Leffall. "But as long as I have been part of the national I have received the greatest support. And I think it is genuine."

He poses with HEW Secretary Joseph Califano and with entertainer Lena Horne, who works with the cancer society. He plays tennis with Andrew Young and Vernon Jordan. He fits each role.

Yet there's a dual purpose to the pushing and the pace, the travel to nine countries so far for ACS, including Russia, and a future agenda of six, including Liberia next week.

"I'm getting the message across about the causes of cancer, the human role needed for family and physician," says Leffall, the voice always steady, never falling from its high pitch. "But I'm letting them know about the in creased risks of cancers in blacks, the treatment and involvement of blacks. I enjoy the role. Sometimes, and Leffall's voice carries an air of defiance, "I go to meetings just to show a black physician can present a topic."

He sits back, the room quiet. The pressure is the same over and over. "I can't afford ever to do less than the best. I don't mind being the first, but I don't want to be the only. But I can't afford to be second-rate."

His son LaSalle Leffall III, now 16 and a student at St. Albans, is facing the same challenges, a world where his father's position and comfortable living gives him experiences few teenagers have. "Because of the world he has been brought up in, he thinks of people as human beings. He knows he's black, and I'm grateful for that, and we discuss the signs of racism. I tell him if this happens, you have to face it, and go ahead and show you are better than the situation."

Leffall is pleased with his own life, but doesn't think he measures up to the men he has most admired in recent years, men he saw make courageous decisions, like John Kennedy, Lyndon Johnson, Martin Luther King Jr. and Muhammad Ali. "I often wondered when Ali refused to go to the war because of his religious beliefs, knowing he would just have to give a few exhibitions...

"I wondered about the price of courage. I wondered if I would have that courage, I don't think so."