"Honor and Intimacy," an exhibition of drawings by winners of the highest award professional architects in this country can bestow upon their colleagues -- the Gold Medal of the American Institute of Architects -- is an immensely pleasurable show.

The first Gold Medal was awarded in 1907 to an Englishman, Sir Aston Webb. Since then 44 architects have been so honored. Consequently the exhibition, on view at the Octagon Museum, provides a relaxed, episodic review of changes in architectural ideas, materials and styles in the western world during the 20th century. But the greatest sources of its charm are the drawings themselves, which collectively afford a privileged glimpse into the nature of the architectural enterprise.

Curiosity is one reason architects draw: to test an idea, to see how it will look. Showmanship is another: to persuade someone to spend the money to turn an idea into a solid fact. Necessity is a third: to explain to a craftsman or a builder exactly how it must be done. From the merest sketch to the skilled presentation piece to the detailed "working drawing," the exhibition contains examples of each type, and each offers its own particular reward.

Among the sketches on view, none is more revelatory, vis-a -vis the final product, than I.M. Pei's famous first notations -- accomplished on a plane ride back to New York 17 years ago after a meeting in Washington with Paul Mellon and J. Carter Brown -- of floor plans for the proposed East Building of the National Gallery of Art. These drawings are not beautiful, but they are brilliant, for in them Pei solved the problem of how to fit two very different uses -- a museum and an office building (for the gallery's staff and its Center for the Advanced Study of the Visual Arts) -- onto a prominent, odd-shaped lot next to John Russell Pope's neo-classical masterpiece. (To this day I have a hard time referring to Pope's great structure as the "West Building." It is still, basically, the National Gallery to me. Pope, for some reason, never won a Gold Medal.)

Pei's unusual geometrical solution, of course, was to squeeze two interlocking triangles, one for each use, onto the trapezoidal site. The design has taken on an air of inevitability over the years, but these alacritous little drawings take us back to its origins as an inspired product of the human mind. It is fascinating, also, to observe the architect as he wrestles with the consequences of his own ideas. He seized the opportunity his geometry provided to create those dramatic, diamond-shaped "tower galleries," for instance, but realized their unconventional shape would present problems for the display of art. "How to subdivide?" he asked himself in a hurried scribble, next to sketches in which he begins to answer his question.

Louis Sullivan's initial 1913 sketches for a bank in Grinnell, Iowa, are on a par with Pei's. Sullivan gave this little bank one of the more beautifully ornamented portals in history, and basically he did it in a few hours of intense thought, sharp-pointed pencil in hand, as these yellowing drawings show. Sketched on a note pad purchased from the Storm Pharmacy across the street from the bank site (the store's name is printed on the top of each sheet), the drawings are clear evidence of a master working at peak speed and assurance.

Louis Kahn's 1967 drawing of the vaulted rooms in the Kimbell Art Museum in Fort Worth demonstrates how concerned he was with natural light and with spaces scaled just so in order to give dignity to their human visitors. We see the playful Philip Johnson at work in 1948, during what is customarily thought of as his deeply non-playful International Style period, trying out different ideas for his famous glass house in New Canaan, Conn. Many viewers may be surprised, as I was, to see that Johnson even then was attracted to the possibilities of historical allusion. The title of one sheet -- "Scheme XX, Syrian Arch" -- says it all. Charles Follen McKim, the great architect who originated the idea of the Gold Medal (fittingly, he was awarded the second medal, posthumously, in 1909), quickly sketched out a front elevation for the University Club in New York that, despite its lack of detail, closely prefigures the palazzo-like finished results. To complete his designs in his busy later years, it was McKim's habit, we are told by architectural historian Richard Guy Wilson in the catalogue, to "sit down at a draftsman's table, usually in his hat and immaculate shirt sleeves, and design out loud." The system obviously worked.

My, how elegantly architects drew back then. They were taught to do so in their schools -- architectural education being based largely upon the model of the Ecole des Beaux Arts in Paris, where the ability to draw well was essential to success -- and many of them obviously took lifelong pleasure in exercising these hard-earned skills. Even those who, like McKim, did not often draw, could count upon a supply of gifted younger draftsmen turned out by the educational system.

Predictably, drawings by architects of the Beaux-Arts era are among the esthetic high points of the exhibition: Webb's stunning perspective rendering in ink of his 1898 design for the South Kensington Museum in London, as sure in its mastery of flickering light as any J.A.M. Whistler etching; Sir Edwin Lutyens' 1913 sketches for the Viceroy's House in New Delhi, which definitively demonstrate his ability to visualize the way the great house would sit splendidly in blazing light upon a hill; enormous scale drawings of the Lincoln Memorial from the office of Henry Bacon; an infinitely skilled pen-and-wash drawing, by an unnamed specialist, for George B. Post's 1894 neo-classical Bank of Pittsburgh.

One can make too much of the oft-lamented decline in architectural drawing (and also of its oft-heralded comeback in recent years). Modernist architects did indeed, as Wilson states, consider drawing a frill -- they saw it as an integral part of the vast Beaux-Arts house of historical styles they wanted to tear down. But in retrospect it seems more a change of style than substance.

Like their elders, Modernist architects still had to put pencil or pen to paper in order to visualize their ideas, and many of them did so with surpassing inventiveness and skill. Witness Johnson's precise, airy pencil rendering (on vellum, no less) of a corner I-beam for the glass house, a piece of work clearly done in thrall to Mies van der Rohe's famous dictum, "God is in the details"; or Herbert Bayer's sharp, convincing rendition of a streamlined interior conceived in 1930 by Walter Gropius; or the single sheet of sketches by Le Corbusier, who was one of the more imaginative and prodigious architect-sketchers in history; or even the strikingly complex perspective renderings of the "Pyramids at the Louvre," accomplished last year by a computer in the office of I.M. Pei.

In its own way this computer drawing is as beautiful, and certainly as informative, as any in the show. This tells us something important about architectural drawings: No matter what their intention, technique or style, their surpassing worth is the light they shed upon the creative process of getting buildings built.

"Honor and Intimacy" will remain on view at the Octagon, 1799 New York Ave. NW, through March 24 (open from 10 a.m. to 4 p.m. Tuesdays through Fridays, and from 1 to 4 p.m. Saturdays and Sundays). The catalogue, with an essay by Wilson and reproductions of many of the works, costs $6. Wilson, who also authored an informative history of the AIA's highest award ("The AIA Gold Medal," McGraw-Hill, 245 pp., $50), will deliver a lecture on the subject at 8 p.m. Thursday in the AIA headquarters building, 1735 New York Ave. NW (admission $3).