MOST of the German Expressionist paintings on display at New York's Guggenheim Museum are painted shrieks. A few are shrieks of joy. Most are shrieks of protest. Some are shrieks of foreboding -- premonitions of terrors to come.

The terrors came. But even after two world wars and Hitler's Holocaust -- after ruined cities, genocide and torture have become part of modern civilization -- these paintings, with their violent colors and raw forms, still make a haunting impact.

In the first two decades of this century, 18 artists created the 140 paintings, 70 watercolors and 120 prints on display at the Guggenheim to shake things up, to stir their viewers. The works share a furor Teutonicus that makes the French Fauves ("wild beasts") of the same period (Matisse, Derain, Vlaminck) look tame by comparison. Only Van Gogh and Edvard Munch can match the German passion.

The German Expressionists as a group are still comparatively little known in this country, except for Wassily Kandinsky, Oscar Kokoschka, George Grosz, Max Beckmann and Lyonel Feininger.In Germany before Hitler, every adolescent with artistic pretensions had a reproduction of Franz Marc's "The Tower of Blue Horses" pinned over his or her bed. Yet in America, even aged art historians, with or without pretensions, have barely heard of Marc, who was killed in World War I at the age of 36.

The Guggenheim show is likely to change that. Entitled "Expressionism -- A German Intuition, 1905-1920," it is perhaps the largest and surely the most important exhibition on the subject in this country. (It will remain in New York through Jan. 18, and then travel to San Francisco.)

The German Expressionists are presented as a cohesive group with a collective goal and message, rather than as individual fellow-travelers

Most modern painting "aimed at an immediate confrontation with reality, unburdened by tradition or history," writes Paul Vogt in the exhibition catalogue. But the Germans did not abandon reality. They transformed it. They criticized it. They burdened it, as it were, with the ugliness and some of the evil they saw or felt: bourgeois hypocrisy under the Kaiser; the inevitability of war and destruction; landscapes defiled by new factories; people corrupted by turmoil. But by criticizing reality and conjuring horrors that were yet to happen, they also thought they could reform and avert. They sought salvation painting, much as the Bauhaus -- founded in 1919, about the time this exhibition ends -- sought salvation in the design of tubular steel furniture and prefabricated workers' housing.

Vogt, who is director of the Folkwang Museum in Essen, the chief guardian of German Expressionism, selected the exhibition, with the help of other German scholars, mostly from European collections. The show is neatly organized into four major groupings: the North Germans; "Die Bruecke" (The Bridge); "Der Blaue Reiter (The Blue Rider); and the Berliners.

The North Germans, in their flat marshes and dunes, were the loners, most deeply influenced by the Norwegian Edvard Munch and the Dutch Van Gogh (also northern loners). They remained deeply involved with their landscape and their peasants, even as they registered their protests against academic luxury art.

The most lyrical painter in this group is Paula Modersohn-Becker, who died at the age of 31. The most powerful member of this group is Emil Nolde, whose "Dance Around the Golden Calf," with its orgiastic colors and frenzied nudes, most vividly expresses both the protest and the hope for which Expressionism stands. "Candle Dancers" conveys much the same idea in a woodcut.

"Die Bruecke" was a brief association of painters around Ernst Ludwig Kirchner, Erich Heckel, Karl Schmidt-Rotluff and Otto Mueller who considered themselves the bridge between a no longer tolerable conventional art and unknown art of the future. Heckel's "Dilborn Park," a fierce landscape, expresses the simultaneous foreboding of doom and (in a small tree reaching for the clouded sun) the expectation of salvation that characterizes the movement. Otto Mueller's female nudes, recurring in oils of a muted palette and lithographs of sparse lines, express a newly found, joyous sensuality.

"Der Blaue Reiter" was headed by the Russian Wassily Kandinsky, who lived in Munich after 1896. The most prominent members of the group were Franz Marc and August Macke (both killed in World War I) and Alexey von Jawlensky. The composer Arnold Schoenberg was the musician in the group. The name was selected because Kandinsky liked the color blue and Marc liked horses and riders. They were somewhat more concerned with formal theories of art than Die Bruecke. But their spiritual agitation was nevertheless concerned with human mysticism and imagery.

Marc's "The Unfortunate Land of Tyrol" -- showing graveyards, burning buildings, starved horses and a poised vulture -- illustrates the prophetic intuition of the group. It was pained in 1913, a year before World War I shattered illusions of peace and prosperity.

The fourth group, the Berlin Expressionists -- Oscar Kokoschka, the American Lyonel Feininger, Ludwig Meidner, George Grosz, Otto Dix and Max Beckmann -- was urban, fraught with social and political agitation and, particularly in the case of George Grosz, bitter satire. The Berliners are best known in this country -- perhaps in part because Feininger, Grosz and Beckmann fled to this country and worked here; and in part because Berlin of the '20s now enjoys a special fascination for the American intelligentsia.

In the Berlin group, too, we find an uncanny prophesy: Why did Ludwig Meidner feel compelled in 1913 to paint a violent yet heroic canvas of "Revolution" five years before it happened?

It is strange that it should have taken so long for the Berliners' northern and southern German colleagues to make it in America. It was not for lack of trying. The late, German-born American art historian William R. Valentiner, who successively headed the museums of Detroit, Los Angeles and Raleigh, N.C., labored tirelessly as early as 1922 to introduce the German Expressionists to this country. His first big effort, an exhibition in New York in 1923, was delayed for several months because U.S. Customs officials confiscated several Kandinsky paintings as unfit for American eyes.

When the show finally opened the New York Times art critic complained, "German artists have not discovered that the war is over, for seemingly this attempt of the individual to make his voice heard above the din of battle results in a loud-voiced cacophony that is most disturbing."

In a sense, the gentleman was unwittingly correct. The war was indeed not over, but followed by World War II. Historians will view both wars as well as the civil war within Germany -- as one continuous upheaval. In that upheaval, the German Expressionists did have a hard time being heard. What they offer is disturbing.

But it is exciting art.