"The 45th Biennial: The Corcoran Collects, 1907-1998" could put an end to 90 years of Corcoran Biennials.

But it probably won't.

After postponing the 1997 version of this contemporary American paintings show to rethink the biennial's future, the Corcoran has put up a show of works from past biennials -- a biennial of biennials, the best acquisitions from a century of biennials.

The show starts in the present with paintings by Philip Pearlstein and Sean Scully and moves back in time, past works by Josef Albers, Edward Hopper, William Glackens, John Sloan, Maurice Prendergast, all the way back to Cecilia Beaux, John Singer Sargent, Mary Cassatt and Winslow Homer. All of these works were acquired from past biennials, either by direct museum purchase or by donation.

The idea propelling Corcoran Director David Levy and Assistant Director Jack Cowart was to take a look at how meaningful these increasingly expensive, time-consuming, controversial and sometimes pointless shows have actually been for the museum.

It turns out to be a brilliant idea. Especially for the Corcoran, where a great but too-little-seen collection has been crying out for liberation from the storerooms. The show offers a new reading of the collection on several levels: as art history, social history and the history of taste. But at its core, this is a story about building a modern collection in a conservative town.

The central revelation here is that the Corcoran Biennials have, indeed, played a profoundly meaningful role in the growth of the museum's American collection, one of the nation's finest. As the Corcoran's most consistent program for acquisitions, the last 44 biennials have swelled 20th-century holdings in American painting by 230 works -- 20 percent of the current total.

In some cases, including those of Homer and Cassatt, these are the only paintings by particular artists that the Corcoran owns. And while two-thirds of the less distinguished biennial purchases are often relegated to storage, and rarely shown, close to half of the 130 paintings in the present exhibition hang regularly with the museum's permanent collection.

Alfred Barr, the legendary first director of New York's Museum of Modern Art, once said that if 10 percent of what you buy for a museum ends up on the walls, you've beaten the odds. By that measure, the Corcoran's jurors, directors and curators, despite all the institutional Sturm und Drang, have done considerably better than we might have thought.

The biennials were originally conceived in 1906 by Corcoran Director Frederick B. McGuire, citing three goals: to awaken public interest in the Corcoran Gallery and Corcoran School, founded in 1869; to benefit contemporary American artists; and to "be instructive and interesting to art lovers, students, and the public at large" -- one respect in which the Corcoran's and other biennials (in New York and Venice) have failed recently.

On Feb. 6, 1907, the "First Exhibition of Contemporary American Paintings" opened at the Corcoran with a white-tie preview attended by President and Mrs. Theodore Roosevelt, members of the Cabinet, congressmen, ambassadors, military brass and cave dwellers. Some of the 13 paintings purchased by the Corcoran from that show -- among them Homer's "A Light on the Sea" and Childe Hassam's "Northeast Headlands -- New England Coast" -- hang at the start (or finish) of this roughly chronological survey (which actually runs backward, starting with the most recent biennial purchases).

Two thousand people a day came to see that month-long show. They spent $49,000 on paintings. By 1928 and the 11th Biennial, sales reached $500,000, close to $5 million in today's dollars. The Corcoran was one of the big buyers, purchasing six of the 297 paintings sold. Among them were two gems by Arthur B. Davies, the dreamy symbolist nude "Stars and Dews and Dreams of Night" and a landscape, "The Umbrian Mountains." They look better than ever here, amid works by less daring contemporaries.

By then, hints of European modernism were finally creeping into the biennials. It was high time. The Armory Show, after all, had introduced avant-garde European art, including abstraction, to American audiences 15 years earlier.

American impressionists were plentiful and prolific, and for years were great favorites of Corcoran juries (on which many of them served). Stylistically retro as the American impressionists were by then (Cowart's short catalogue essay is appropriately titled "The Corcoran Biennial During the 20th Century: Retro or Radar?"), they represent the largest presence here by far. Most are pleasant landscapes or intimate interior scenes with ladies embroidering, writing or rocking a cradle. (One young woman, curiously, walks around carrying a fish.)

Among the more memorable of these impressionist works are those by Edmund Tarbell (who was in two biennials), Hassam (who was in three), Daniel Garber (three) and Edward Redfield (four). Emil Carlsen (three) stands in high relief here with "Moonlight on a Calm Sea" (1915), a silvery seascape that verges on total abstraction and recalls the work of one of Duncan Phillips's favorite painters, Augustus Vincent Tack. The unfamiliarity of most of these works yields many agreeable surprises, including "Monadnock," a fine 1912 mountainscape by Charles Woodbury.

There are also portraits, chief among them Beaux's "Sita and Sarita" from the Ninth Biennial in 1924. One of the greatest paintings the Corcoran owns, it focuses on a dark-haired young woman whose beautiful green eyes are rivaled by those of the black cat standing on her shoulder. Someone at the Corcoran seems to have had a passion for cats, since two others are also featured in portraits here, one in an oddball picture by George Luks, the other by one Peppino Mangravite.

Cowart calls his installation of this seven-gallery show "crypto-chrono-thematic," which explains why the chronology gets confusing at times. But a fine illustrated catalogue has been published for those who want to follow the history more precisely.

It is, however, roughly chronological, though as noted earlier, it starts with the newest acquisitions and moves backward, which has its compensations: This way, the show keeps getting better and better.

It begins with a a small, overcrowded space filled with abstract paintings.

Wholly abstract paintings turned up late in the Corcoran Biennials (at least as presented here), finally making inroads in the late '50s. But purchases were way off the mark: A room label claims that they were showing abstract expressionists at the time. What we see are hopelessly dated-looking abstractions by Rico LeBrun, Sue Fuller and others.

Yet there are fine examples, too: by Albers, Burgoyne Diller, Will Barnet and Joan Mitchell. And there is an exceptional room of '70s and '80s abstractions by Ron Davis, Joan Snyder, Harvey Quaytman and Robert Mangold, the last a superb painting acquired in 1987 by Corcoran curator Ned Rifkin, who also brought the museum its large Scully. A painting by Sandy Sloan, shown in the '76 Biennial and recently donated to the Corcoran, holds its own, even in this distinguished company. Overall, recent abstraction is well represented at the Corcoran.

There are also glaring absences: New York abstract expressionism, apparently, never made a dent in the collection until the late '60s, apart from one mediocre painting by Larry Rivers. A room label claims that "Abstract Expressionism had become a staple of the Biennials by the 1950's," but where is the evidence? Pop is also totally absent, unless you count the pop-inspired veneer on the otherwise dead-in-the-water academic nude by Pearlstein.

Most incredibly, even the Washington Color School -- the only art movement with Washington's name attached -- failed to make inroads through the Corcoran Biennials. And as a result, there is no Morris Louis here, no Ken Noland, no Howard Mehring or Tom Downing. (Works by these artists, however, have since entered the collection, as has a painting by Willem de Kooning.). The only color field painter whose work was acquired from a Corcoran Biennial was Jules Olitski.

As you move along, you're likely to be stopped by Sloan's wonderfully nostalgic "Yeats at Petitpas" (which in mood recalls Renoir's "Boating Party"), and Hopper's small but fabulous sailing picture "Ground Swell."

Things culminate in the final gallery, which contains not only Homer's haunting "A Light on the Sea" (1897) and Cassatt's "Susan on a Balcony Holding a Dog" (1880), but also Sargent's fabulous landscape "Simplon Pass."

Over the years, every conceivable variation has been explored to solve the myriad problems inherent in such survey shows. To please the public early on, there was even a $200 people's choice award, chosen by public ballot: The choice never coincided with that of the judges. A frequent winner was Gary Melchers, actually a fine painter, but represented here by an altogether goofy painting titled "The Smithy." The painting was given to the Corcoran by Duncan Phillips, who, for obvious reasons, didn't keep it for his museum.

In 1967, the increasingly unwieldy juried shows were abolished in favor of more focused exhibitions put together by museum directors or curators. How have they fared as seers? That information, too, can be ferreted out of the exhibition catalogue, which is full of facts, and a high-water mark in recent Corcoran publications. Suffice it to say that even the best of them have come up with some clinkers.

Terrie Sultan has had the most recent challenges, in these pluralistic times. But she has managed, in three biennials, to convey some sense of what's been going on in painting, especially in the last show, "Painting Outside Painting."

It dealt with the current impulse to use nontraditional media as well as paint and canvas. And one acquisition from that show, Jessica Stockholder's "1994" (which I did not understand at the time), has taken on special meaning in the context of the current debates over the biennial's future. A messy, three-dimensional construction made from plastic sink legs, yarn, clothing, plastic fruit, wallpaper, etc., it looks like a painting that, powered by its own inner forces, finally exploded into a sculpture.

It may not be a great work of art, but it points to the constraints imposed by biennials that have never recognized any form of expression outside painting.

In his catalogue introduction, Corcoran Director Levy writes: "Today, some 90 years after the Corcoran mounted its first Biennial, we have to ask whether the impact of such exhibitions has been so drastically altered by the changed environment . . . as to make them anachronistic."

According to Levy and Cowart, the question of whether the biennials will continue is still open. But scrutinize their catalogue essays -- along with that by Sultan -- and they all seem to say the biennial should continue, but in a more flexible form. Exactly what that means, however, will be the subject of public debates that the Corcoran plans to mount between now and and Sept. 28, when the 45th Biennial closes.

At present, there is one more biennial on the Corcoran's books: for 2000. Cowart is determined it will take place. "There will be a millennial biennial in 2000," he says. NOT LIKE EVERY OTHER YEAR

"The 45th Biennial: The Corcoran Collects: 1907-1996" will be on view at the Corcoran Gallery of Art through Sept. 28. A highly informative, fully illustrated catalogue of the exhibition, including a history of the Biennial exhibitions, is available in the museum shop. The Corcoran, at 17th Street and New York Avenue NW, is open 10 a.m. to 5 p.m. (except Tuesdays), and Thursday evenings until 9. There is no admission fee: Suggested contributions are $3 for adults, $1 for students and seniors, and $5 for families. For information call 202-639-1700. CAPTION: Cecilia Beaux's "Sita and Sarita," above, and Winslow Homer's "A Light on the Sea," below. ec CAPTION: The oil-rich Corcoran shows Arthur B. Davies' 1927 "Stars and Dews and Dreams of Night," above, and Edward Hopper's 1939 "Ground Swell" at its biennial. ec CAPTION: Mary Cassatt's 1880 "Susan on a Balcony Holding a Dog," above, and Robert Mangold's "Five Color Frame Painting," 1985. ec CAPTION: The opening celebration of 1939's biennial. ec