Every now and then an exhibition comes along to alter what we value, to change the way we judge the painting of our time. One such catalytic show -- passionate, important, idiosyncratic -- goes on view today at the Hirshhorn Museum.

"Representation Abroad" revives the viewer's faith in unmarketable art. Few dealers will get rich peddling these pictures, these odd compelling portraits and hallucinatory still lifes. They took too long to paint -- some required years -- and they take too long to see.

The big-time, big-bucks art biz depends on big-name artists. But of the 16 painters chosen by Washington's Joe Shannon, only England's David Hockney is famous. The others come from Hungary, Colombia, Israel, Australia, from Naples, Madrid, Glasgow, London and Berlin. Not one relies on glitz.

Shannon is not battling the splashy New Expressionism now so much in vogue. A number of his painters -- Switzerland's Luciano Castelli and Berlin's Wolfgang Petrick -- seem to embrace it. What separates these two from other New Wave painters, and what allies them to the other painters here, is that they can draw. It is hard-won and unbluffable and eye-convincing drawing that unifies this show.

Too much newish New York art tries to do it all at once, tries to seize the eye as quickly as a red light or a subway ad. One never feels that here. These paintings demand patience. They slow the act of viewing.

Much marketable art today, draining the last dregs from the modernist tradition, yearns to shock the viewer, strives to have him ask, "Could this possibly be art?" Here one rarely wonders. The high skill of these painters, the patience in their pictures, their loyalty to drawing, and their astonishing ambitions, rarely lets one doubt.

Painters not so long ago -- modernists at least -- sought the wholly new and made war on the past. But that war is ending. The past is back, if only to be ransacked. A door has been thrown open. The painters here walk through it, but unlike Oldenburg and Warhol, who grabbed the hamburger, the soup can, and unlike David Salle, who also appropriates the cheap and the commercial, they do not pursue the trashy. Instead they seek the high ground, they struggle to attain the peaks seized long ago by Caravaggio, Vermeer, van Gogh and Ce'zanne.

The 20th century is almost over. In the century to come, three of Shannon's artists -- Hockney, Israel's Avigdor Arikha, and Madrid's Antonio Lo'pez-Garcia -- are likely to be counted among the most accomplished painters of our time.

Hockney is a shape-shifter, a protean inventor. His three-wall exhibition here demonstrates succinctly how his late experiments with Cubism and cameras have forced time into his paintings. Arikha's finest pictures glow with terrifying modesty, with transcendental plainness. They are wholly unaffected. His brush flicks back and forth, restlessly, insistently, with no trace of bravura, and yet from those bland brush strokes stunning faces rise. There is within his art a near-unbearable intensity. To stare into the cool blue eyes, or at the tangled locks of his androgynous "Marie Catherine" (1982) is to glimpse Medusa. One's blood chills.

Arikha completes each of his paintings at a single sitting. A day is not enough for Lo'pez-Garcia. His art requires years.

If he "starts a landscape at 5:00 a.m. in the spring of a given year," writes Shannon, "the work most likely will not be completed that year . . . The painting will be put aside as the summer light comes on. The next spring, when the same weather returns, the work is taken up again."

No one who encounters the paintings and the drawings of Lo'pez-Garcia will doubt he is a master. Why is he not famous? I cannot recall when I last encountered an unfamiliar painter as good. He is no photorealist. The "reality" of the photograph is drained, is turned to triteness by the suprareality of his "Mirror and Basin." The rust stains on the sink, the bristles of the shaving brush, the gleam of the chromed faucets -- each tiny mundane detail has a magical intensity. The perspective that's obeyed by the top half of the painting is not that of the bottom. His little exhibition here astounds the viewer often. Look at the light bulb burning in his pencil drawing of his littered studio. Look at the way the shoulders and the head of his "Woman in Bath" (1968), and the greenness of the water, are reflected in the glaze of the tiles by her tub. Were Shannon's exhibition less considered, less seamless and coherent, Lo'pez-Garcia would steal the show.

Isabel Quintanilla, his Madrid colleague, is another extraordinary artist. She, too, relies on antique skills and painstaking depiction, and yet her work, like his, rarely feels old-fashioned. Look at how she paints a dead fish on a tablecloth, or a bottle of red liquid placed before a window. Something wholly modern, an ache, an alienated presentness, activates her art.

Tibor Csernus, a Frenchman born in Hungary, is another painter who has reached into the past to make art of the present. He has apprenticed himself to Caravaggio. He has studied that master's shadows and mood of intense drama, but his theater is a theater of our time.

Glasgow-born Leonard McComb is a visionary painter, a seer of the unseen, a kind of modern William Blake. Once, when still a child, Blake yelled to tell his mother that God had pressed His forehead against the window pane. One feels something as mysterious, a looming toward the all, in McComb's enormous half-transparent nudes. His colors are those used by Ce'zanne. His form-defining brush strokes call to mind van Gogh's. And yet the whole ensemble is entirely his own.

Luis Marsans lives in Barcelona. His delicate, small, Peto-like still lifes have a softness that suggests centuries of aging, but their familiar props -- a Bic pen, a Bic lighter, a bright red can of Coke -- are artifacts of our time. Or were until just yesterday. The Coke can has been changed. These small pictures on panel, have been, before our eyes, turned into antiques.

Other impressive pictures -- a large and quickly painted Nino Longobardi canvas with skulls and rhinos, Rodrigo Moynihan's painting of a light bulb, the half-wry, half-amusing self-portaits of Juan Ca'rdenas, Klaus Fussmann's haunting "Nude in Front of a Mirror" and Arthur Boyd's "Birth of Narcissus" -- turn up throughout the show. One of the most memorable is Luciano Castelli's "Venice by Night" (1984), a vast, erotic canvas flecked with gold and dark with night.

Shannon's personality pervades his show. Few professional curators would have dared put it together. But Shannon, though a curator (he previously arranged Hirshhorn exhibitions of the paintings of Edwin Dickinson and R.B. Kitaj), is not a curator only. He's a painter. Those who know his pictures -- with their self-portraits and monsters and erotic confrontations -- and those who have admired his highly assured drawing, will understand at once the spirit of this self-portrait of a show.

He might have chosen a dozen other painters. Instead he has followed the dictates of his heart. A sense of personal involvement gives this show a good part of its power. His catalogue entries are not the usual dry and dull assemblages of facts; they read like small short stories.

Sandra Fisher, Kitaj's wife, is among the artists he knows well and admires. She sent him a description of her pastel portrait of "Louise" (1980):

"Two weeks after the pastel was finished, she committed suicide by throwing herself off a bridge into the sea because of her love for a young man . . . and to this day I still feel strong grief and anger at this talented and intelligent girl of 17 throwing her promising life away."

"So now you know," writes Shannon, "how much more meaningful the image has become with this 'inside' knowledge."

When Shannon writes that "Arikha applies paint with volcanic scrubs and whacks, disintegrating hog's hair flat and round brushes alike," or discusses McComb's "gold ochres, Naples yellows and umbers," we hear a knowing painter speaking about painting. He cares. He cares for every artist and object in his exhibition, and he demands that we care, too.

His exhibition has another major virtue. Shannon, who 10 years ago was hired by former Hirshhorn director Al Lerner to design exhibitions, knows every inch of that museum's temporary exhibition space. His show, not surprisingly, has been flawlessly installed.

It is a shame that "Representation Abroad" (its title, too, is fine) is not going to New York. It would have given that city a most useful jolt. It will remain on view all summer and will close Sept. 2.