As the principal designer for the remarkable firm of Skidmore, Owings & Merrill for more than three decades, Gordon Bunshaft, who died last week at age 81, was a presiding officer of a momentous change of architectural taste and practice: In the postwar years he helped mightily to lead corporate America, and with it much of the world, to embrace modern architecture.

His legacy, thus, is both good and bad.

Like the early modern architects who influenced his approach, Bunshaft believed that the new technologies and materials of the 20th century demanded new building forms and unencumbered architectural expression. The difference was, he lived at a time when these technologies and ideas actually could be put to use on a large scale, and with his major clients he proceeded to do so in structures of unusual concision and clarity.

"It was a most exhilarating time to be an architect," he later would reflect. "I'm glad I was born when I was, so I could be a part of it."

Bunshaft's best buildings as a rule are visually quite simple -- one feels that one can grasp what they are about at first sight. Think, for instance, of the cylindrical Hirshhorn Museum (completed in 1974), his only Washington building, or of the Lever House (1952) in Manhattan, the still astonishing all-glass sliver. Or the splendid translucent grid of the Beinecke Rare Book and Manuscript Library (1963) at Yale University, or the inspiring sequence of tentlike structures at the Haj Terminal (1981) in Jiddah, Saudi Arabia.

And yet these appearances can be deceptive. The buildings almost always reveal further delights and complications upon close inspection -- the glazed circular sculpture galleries inside the Hirshhorn ring, the outdoor terrace on the Lever House's third floor. Or the extraordinary below-ground Zen garden (with sculptures by Isamu Noguchi) at the Beinecke, the exemplary structural engineering (by SOM's resident super-engineer, the late Fazlur Kahn) at the Haj Terminal.

Simple appearances tend to mask, too, the sophistication of the SOM enterprise. The firm contributed exacting standards not only for structural innovation and excellence but also for precision and craft in detail, and for livability in the corporate work place. As did (and do) many modern architects, Bunshaft liked to maintain that his primary job was that of a sort of advanced technician, solving problems for his clients. And he did it well in both city and suburb. In particular, his buildings for the Connecticut General Life Insurance Co. (1957) helped to establish a new if still debatable pattern for campuslike corporate compounds.

But such claims to technocratic anonymity struck a false note. Bunshaft was a talented, decisive, stubborn designer, known for adopting an aesthetic model early in the design process and sticking to it. Though hardly an innovator in the class of, say, Ludwig Mies van der Rohe or Le Corbusier, two of his modernist exemplars, Bunshaft fit the mold of the artist-architect, and his search for the bold, the clear and the unique "solution" sometimes resulted in willful idiosyncrasy.

One of the worst examples of this was the Lyndon Baines Johnson Library (1971) in Austin, Tex., an overblown, stentorian exercise, surreal in scale, dwarfing in effect. The Hirshhorn is not in this class as a prideful mistake, but despite its virtues its geometry is unforgiving -- as we know well by now, the circulation system in general is rigid and that of the painting galleries is especially confining.

Bunshaft's conception of each building he designed as unique, as separate from its larger setting, is a fault he shared widely with architects of his generation. In his case the fault is magnified because he rarely worked on anything but a very big scale. Notable exceptions include the Manufacturers' Trust Co. branch bank (1954) on Fifth Avenue in Manhattan, one of the best little urban glass boxes ever built; his own house (1963) on Long Island, a pristine white box-in-a-field; and a wing for the Albright-Knox Art Gallery in Buffalo (1962), an unforgettable jewel-like reprise in dark gray glass of a fine neoclassical temple on a hill.

Even the little buildings tend to prove the rule. Both the house and gallery wing exist more or less in splendid isolation -- nature provides a sharp, pleasing contrast. As pretty as it is, the branch bank stands apart from the surrounding city and implies radical surgery on the cityscape. Which did transpire, of course, in certain parts of Manhattan, and the world. The irony has often been noted that the urban glass box loses lots of its attraction when it mirrors only other glass boxes.

Bunshaft, of course, cannot be castigated for the particular miscues of lesser architects with less prestigious clients. But by setting such a sterling example he certainly did help to clear the table for major mistakes on a citywide scale. Bunshaft's big urban buildings shout for attention; many of them richly deserve it on formal and aesthetic grounds. The triangular tower he did for the National Commercial Bank (1983) in Jiddah, for instance, is a beautiful abstract apparition, but it is wildly out of scale with the packed, low city that surrounds it. Nor can one believe from photographs that it is at all in keeping with the rhythm of Jiddah streets.

Even in towering New York, Bunshaft made the same kind of mistake. The mid-block skyscraper at 9 W. 57th St. (1974), with its swooping profile of dark glass and its exposed steel wind braces, does indeed make a dramatic image. But it is an unfortunately reproducible feat -- I saw its like in Seoul in 1988 -- that flouts convention at substantial urbanistic cost. At ground level it's practically scaleless, possessing none of the colorful busyness that makes Manhattan streets so attractive. Even from afar it seems overpowering. It is monolithic. The architect bragged that when built it was "probably the flattest large glass surface in the world."

Bunshaft the man was widely admired -- his talent and professionalism were never in question -- and his younger colleagues at SOM, understandably, viewed him with awe. Carol Krinsky, in her recent biography, tells that visitors to SOM's New York offices in the 1960s observed the younger men, coterie-like, affecting the master's ways down to suspenders and pipes. As a design critic he was widely feared, and rightfully so. His cranky, brusque dismissals were famous, although William Walton, chairman of the Commission of Fine Arts when Bunshaft was a member during the 1960s, observes that "he saved his harshest words for his equals, which is a measure of kindness."

Washington may be indebted to Bunshaft for more than the mighty Hirshhorn. According to Walton, it was Bunshaft who conceived the basic formal scheme for the city's Metro stations. The story is vintage Bunshaft. The commission and Metro architect Harry Weese were engaged in a long give-and-take over the design of the stations. On perhaps the third go-round, Walton recalls, Bunshaft impatiently demanded a piece of paper and then and there "drew a great arc, with the platform coming down in the middle of the arc" -- in essence, the final idea. And a noble one.

Bunshaft was born in Buffalo on May 9, 1909, to middle-class Jewish parents who had emigrated from Russia the previous year. A quiet self-starter as a young man, he spent a lot of time building his own furniture. He went to MIT for his bachelor's and master's degrees in architecture, and did brilliantly. In 1937 he met Louis Skidmore, who with Nathaniel Owings had founded a little firm a few years before, and he worked with the company (with time out for World War II) until 1979. However one takes its measure, he left an extraordinary body of work.