FROM THE HERMITAGE in Leningrad and the Pushkin Museum in Moscow, the two largest museums in the Soviet Union, comes an extraordinary experience -- a kaleidoscope of color and form that stays in the mind long after the moment is gone.

At the National Gallery, the 41 "Impressionist to Early Modern Paintings From the U.S.S.R." are more than grace notes to "The New Painting," the Impressionists show that just closed here. Through them, one can sense the sweep toward abstraction -- a giant step, a loosening up, from how things look to how the artist feels about them. As Picasso himself put it, when describing the development of cubism with Braque, "We wanted to paint not what you see but what you know is there."

Monet, Renoir, Ce'zanne, van Gogh, Gauguin, Matisse, Picasso. How did so many of their masterpieces end up in the Soviet Union? In the late 19th and early 20th centuries, two Russian collectors sensed something was afoot in Paris. The two friendly competitors, Sergei Shchukin and Ivan Morozov, were on the ground floor, able to pick and choose. Their collections having been nationalized after the October Revolution in 1918, Shchukin and Morozov in essence were responsible for all the Impressionist, post-Impressionist and early modern paintings in the Hermitage and Pushkin Museums.

With light-infused landscapes, a glistening pond or the Seine, Monet and Renoir present a delightful reprise of the previous show. But with Ce'zanne, things had already started to slip. Some call him the father of modern art, and it's easy to see why. In bold brushstrokes, his country landscape at a town called Pontoise has a flattened perspective, the trees seem too tall, and -- there's no light!

The focal point of Ce'zanne's "Woman in Blue" is not the fleeting effect of light. It is her elbows. She is all angles -- capped sleeves, pointed brim hat, V-necked jacket, and, especially, elbows, that form trianglesin space.

Van Gogh was something apart, and there is one painting here that at once demands your attention while urging you to look away: "The Prison Courtyard." Walled in and beaten down, the men trudge endlessly in a circle. In the foreground van Gogh painted himself, the prisoner without the hat. Feeling trapped, searching for his own sanity, van Gogh painted it while confined to the asylum at Saint-Re'my. From the prison of his own mind, he marked the brick walls and the paved courtyard with stroke after monotonous stroke.

While confined to the hospital in Arles, where he went after his first nervous breakdown, he painted the stunning "Portrait of Dr. Fe'lix Rey," also on display here.

Dr. Rey used the portrait to cover a hole in his chicken house. No wonder it was so easy for Shchukin and Morozov to pull off a coup.

Both collectors went for Gauguins. With nine paintings in the show, Gauguin has the most here. Unlike van Gogh (whose act of cutting off part of an earlobe was precipitated by an argument with Gauguin), Gauguin searched for inner peace by escaping to Tahiti. Here are his seaside reveries, full of play and sensuality, hardly an anthropologist's view of the tawny-skinned natives.

"What, Are You Jealous?" was one of his favorites. In his book, "Noa Noa," Gauguin described the scene: "On the shore, two sisters are lying after bathing, in the graceful poses of resting animals; they speak of yesterday's love and tomorrow's victories. The recollection causes them to quarrel: 'What, are you jealous?' "

Matisse's large paintings are explosions of colors that look edible. Shchukin encouraged Matisse's idea of making paintings as part of a room's design. No doubt Shchukin felt there were two extra people in the room where he hung "Conversation." In the painting, Matisse, wearing pajamas, talks in a relaxed way to his wife Emily. With a window in between, they face each other against a very blue wall that outlines them in hard silhouette, like the paper cutouts Matisse made late in his life. "The Red Room" is another giant-sized tableau -- the maid clearing the table appears to be part of the wall decoration. With its curling blue tendrils against a red background, the painting is like a naive sampler.

The very flat Matisses (there are seven here) contrast with the cubist contouring of Picasso (eight in the show). The most astounding painting in the show is Picasso's "Three Women." The African art influence on Picasso, and the idea that started with "Demoiselles d'Avignon" come to full flower here.

These are three primitive goddesses at their bath. They may be washing their backs -- but they also appear to be stretching, awaking from a dream of creation. Against a green background, they are clay colored, the colors of nature.

"Three Women" almost belonged to the West. Gertrude Stein owned it first. Then Shchukin bought it.

But does it matter who owns it? It is such a strong image that everyone can carry away a piece of it in memory.

Thirty-four of these works are being seen in this country for the first time. This show is the first major art exchange to result from the cultural agreement signed at the Geneva summit. (Armand Hammer provided the funding for the exhibition.) Meanwhile, the National Gallery has sent a comparable show to the Soviet Union. IMPRESSIONIST TO EARLY MODERN PAINTINGS FROM THE U.S.S.R. -- At the National Gallery of Art through June 15. Advance passes are available at a Ticketron Pass Desk in the East Building or at Ticketron outlets. They may also be ordered by calling Teletron, 1-800/233-4050.