IN NONE OF HIS less profound utterances, Frank Lloyd Wright is supposed to have said, "Bill Zeckendorf has a real estate office with a Chinaman in the back room."

William Zenkendorf was the super-developer of the bygone urban renewal era. His firm, Webb and Knapp, launched the redevelopment of Washington's Southwest and built large urban renewal projects in the hearts of Denver, Philadelphia, Montreal and dozens of other cities.

The Chinese-American, who was for 12 years on the staff of Webb and Knapp, is architect Ieoh Ming Pei, who is now way out front and currently being lionized all over town for his design of the National Gallery East Wing.It opens June 1.

Pei's last name is pronounced "pay". Ever since he came to this country from Canton, China, in 1935, his informal first name, the one even his wife uses, has been "I.M." His fellow students at M.I.T. decided that Ieoh could properly be pronounced only by a cat and kept joking about "I am, you are."

Pei was sent to the Massachusetts Institute of Technology at the age of 18 by his father, then president of the Bank of China, who told him to get an education. "I wasn't really interested in becoming an architect," he told me. "My real reason for coming here is that I loved American movies."

He started in engineering but, despite his protests that he could not draw very well, was persuaded by some of his teachers to switch to architecture. He went on to the Harvard School of Design where he worked under Walter Gropius, Marcel Breuer and other apostles of Bauhaus Modernism.

Pei proudly declares himself a second generation Modernist. "Architecture is not a matter of fashion," he said."You cannot have an architectural revolution every 20 years." Mies van der Rohe said we could not have a new architecture every Monday morning. It often seems that we do, however.

But at a time of uncertainty, Pei is quietly sure of himself and his designs. "Architecture," he continued, "is like a tree. It grows and matures and branches out. I am part of that tree, of that movement, not starting, or ending, or following anything."

He does not seem comfortable discussing architectural philosophy. He is busy doing architecture, and does so with contagious enthusiasm. His buildings are consistently strong and decisive.

Only once did Pei attempt to stray from the functional path he was shown by Gropius at Harvard. He drove to Taliesin East in Spring Green, Wis., to see what he might learn from Frank Lloyd Wright. "I drove into the compound," he told me, "and stopped, not knowing where to go. Suddenly seven huge Alsatian dogs pounced on my car and barked and yelped at me. They looked ferocious. I felt trapped. Several students just stood there and laughed. I drove away."

When World War 11 came, it was clear that Pei could not go back to China. Instead he was drafted to work for the National Defense Research Committee. His job was to figure out how best to annihilate Japanese villages and he did not like it very much.

In 1945, Gropius called him back to Harvard to teach. Not long thereafter, William Zeckendorf was looking for a house architect. He inquired at the New York Museum of Modern Art and of Nelson Rockefeller. Zeckendorf felt, according to his memoirs, that "it was about time the modern Medici began hiring the modern Michelangelos and da Vincis." Pei accepted.

Before long, Webb and Knapp had an architecture department of some 70 people, headed by Pei. "We were a great team, each one teaching the other," boasted Zeckendorf. "One of the finest things I ever did was draw my friend (Pei) away from the halls of academe and into the world of building."

The world of building saw with amazement that money-making, speculative development and good architecture were not necessarily contradictions.

One of the "great team's" toughest jobs was turning the tree-lined slum south of the national Capitol into a decent place to live. It started with much enthusiasm, but Zeckendorf's and Pei's plans for Southwest urban renewal soon got bogged down in the bureaucratic morass. Pei wanted to link the urban renewal area more closely to the city, bridging the dividing railroad and freeway, but his original plan was badly compromised. "It all got way out of hand," said William L. Slayton, Zeckendorf's man at the time and later President Kennedy's urban renewal commissioner.

But Denver's Mile High Center, the Place Ville Marie in Montreal (which is similar to Pei's L'Enfant Plaza in Washington) and especially Society Hill in Philadelphia with its three handsome towers were instant commercial and critical successes. Each shows an exceptional sensitivity to its surroundings. Pei understands the social and visual dynamics of the city. His genius for urban design is particularly evident in his plan for Boston's Goverment Center, where others designed the buildings. All of his projects are carefully thought out - and show it. Even Pei's mammoth Kips Bay Plaza in New York City - a housing project of the kind that gave housing projects of the 1950s and '60s a bad name; has an endearing dignity.

In 1955, Pei and his closest associates from his Harvard days struck out on their own. It had nothing to do with Zeckendorf's subsequent bankruptcy. The two remained close friends until the super-developer's death a few years ago. But it gave Pei a chance to branch out from Zeckendorf's kind of work, work which in Europe is called "social architecture."

Two buildings of the 1960s stand out as the most Pei-ish of Pei's buildings: the Green Center for the Earth Sciences on the M.I.T. campus in Cambridge and the National Center for Atmospheric Research in Boulder, Colo. The one is an elegent tower rising above a humdrum array of tightly packed, mediocre structures. The other blends into foothills of the Rockies as a Hopi village blends into the mesa.

A year or so after President Kennedy's assassination, his widow, assisted by her friend, the painter William Walton, convened 18 of the world's most famous architects to select the best possible designer for the John F. Kennedy Memorial Library in Cambridge.

At first, as Walton tells it, they decided at length to rule out Mies van der Rohe as being too old.

Then this Olympus full of architectural deities balked and told one another that they had no business recommending anyone. It was unethical. It was unwise. They were happy to tell Mrs. Kennedy how to build the building (and each was willing to build it himself). Olympus was, after all, not an employment agency.

Walton reminded them that they had a dinner invitation with the senior Kennedys at Hyannis Port. But he would be forced to withhold the tickets until they made their recommendation. They cast secret ballots.

The outcome was a complete surprise. "I counted the votes," recalled Walton, "and they were overwhelmingly for I.M. Pei. It was a vote not for what Pei had done, but for what they felt he was capable of doing. Pei's best work, like John Kennedy's in 1960, was still to come."

"Pei is undoubtedly among the world's three or four greatest living architects," said Hugh Newell Jacobsen, modestly refusing to name the other two or three.

Counting him or herself in (architects are seldom reticent), there are few architects anywhere who would not place I.M. Pei and Partners at the very top of their profession.

His buildings are talked about and remembered, and it is difficult to find anyone who will say anything critical, let alone derogatory, about I.M. Pei or even his firm of about 100 people, some of them outstanding designers. Most noted are Harry Cobb and James Freed. Leonard Jacobson is Pei's associate partner in charge of the National Gallery East Building. Eason Leonard and Werner Wandelmayer manage what, in the eyes of envious competitors, is one of the most smoothly run architectural offices in the country. It turns out about 12 building designs a year.

The most talked about Pei building is the John Hancock Tower on Boston's Copley Square. But it isn't talked about because it is a brilliant or even beautiful solution to a tough design problem. It is talked about because its mirror glass panes kept falling out. The lawyers are having a heyday and until a merry-go-round of damage suits is settled, in or out of court, next year or in 10 years, no one will publicly say what happened for fear of getting caught in the legal whirl.

The Kennedy Library, too, was mostly being talked about for nonarchitectural reasons. It just did not fit into the Cambridge community. A new design, at a new site, is scheduled to be completed next year and likely to bring Pei still more fame.

There is no Pei cult, however, as someone observed, in the sense that there was around Frank Lloyd Wright, or Le Corbusier, or Richard Neutral.

Pei has never claimed that architecture brings salvation. He has no airs about him. As the celebrity he could now so easily be, he is a flop. He has no mannerisms, no quotable quotes, no ostentation.

His office on Madison Avenue, to be sure, is flashy in its austerity - all white, sparse, curvy and indirectly lit. But Pei himself, with his cheerfulness, supplies warmth.

"Pei is charming, decent, humble, humane. He always listens carefully to what you say and remembers. Yet, he's no pussycat when it counts," said Hugh Jacobsen.

"Pei is always supremely cool and always dedicated to higher purposes. He is always responsible and responds to facts. He lets the facts of a situation change his mind if necessary," says associate partner Leonard Jacobson.

"Pei is absolutely delightful to work with. He listens intently to your problems, and then, firmly but graciously, comes up with a solution that invariably evolves from common sense and the dignity of the building," says David Scott, the man in charge of the building program for the National Gallery.

"Pei can spot it if the concrete is off an eighth of an inch 17 stories up," said a construction foreman who worked on the East Building.

Pei may be always that loveable. But by his own account, he is not always that cool. "I get into a great inner turmoil when I have to find the right design for a building," he said. "It absorbs me completely and I can't think of anything else. This may be a matter of hours or it may take as long as a month of sleeping badly, being irritable, sketching ideas and rejecting them. I am useless to everyone else. It is traumatic for my wife."

When Pei has his basic idea clear in his mind and sketched on paper, he gets together with his partners. "That's where the sparks start flying. At times we get very frustrated and have to start over again. We work and work. We worked for five years on the drawings for the East Building." But he does not participate with equal intensity in all projects. Frequently his partners take charge.

Like other prominent American architects, Pei now travels a great deal toa seek and take care of commissions abroad. In one recent week he was in both Hong Kong and Cairo. He is doing buildings in Australia, Singapore, Tehran, Kuwait and London. The traveling tires him. He says it reduces his productivity. But he feels it is necessary to support the firm.

Pei finds his recreation at home with his family, his friends and his exquisite collection of modern art. His wife, Eileen Loo, was also born in China. They have three sons and a daughter. Two of the sons, Chien Chung, 31, and Li Chung, 28, worked in their father's firm. Chien Chung was on the National Gallery East Building team and is now involved with the addition to the Boston Museum of Fine Arts. Li is apprenticing. Both studied architecture at Harvard. The third brother, Ting Chung, 33, is a real estate developer. Pei's daughter, Lian, 18, has just finished highschool and is preparing to go to college. Eileen Pei is a renowned gourmet cook, equally interested in Chinese and French cuisine. Pei is "a wine man," according to Walton. "Wine stewards tremble when they see him entering their restaurants." But eating out, like the small but exquisite parties the Peis like to give for their artist friends, is relegated to rare occasions. Ieoh Ming Pei is not good at being a celebrity.