Often in old Westerns--just before their flashing fists knock the bad guys silly--Hopalong or Cisco, Gene or Roy or Lash LaRue tip their hats politely and say " 'Scuse me, ma'am," or some such. Something just as Western, just as manly, well-mannered and attentive to the audience marks the Corcoran Biennial opening tonight.

Thirty living artists were chosen for inclusion in this vivid exhibition. All paint in the Western states. Most try hard to please.

All of them are modernists. None of them produce the hero-with-a-sixgun art found on the covers of the pulps. Yet there is something of the Old West in the motives they reveal. Many of the best of them share a modest-macho code.

Because they seem to admire, even while distrusting, the art world's "isms," they tend to undercut their trendiness with a self-deprecating humor. They avoid the over-difficult by adding easily read clues to their pictures. A hawk, for no clear reason, shows up in the middle of James G. Davis's Francis Bacon-like abstraction.

A number of these painters, when they fear they're getting prissy, tend to spice their pictures with slightly vulgar jokes. They don't avoid the violent. Denver's John R. Fudge and Fort Worth's Vernon Fisher put A-bombs in their pictures. Charles Arnoldi paints his with a chainsaw. These painters, as a group, refuse to sneer at the observer. Their exhibit isn't haughty. It strives to entertain.

It generally succeeds. This year's Corcoran Biennial recalls those of the '60s. Many of its pictures are big and brightly colored. Most are signed by artists whose names we do not know. With its cubism and cows, its easily read satires and nicely painted surfaces, it is a bold and friendly show.

Although it has two titles, "The 38th Corcoran Biennial Exhibition of American Painting/The Second Western States Exhibition" it is one show, not two. Traditionally, the Corcoran, every other year, mounts a show of paintings that are both American and new. This year, for reasons that are both curatorial and financial, it joined forces with the Western States Art Foundation and took grants from Philip Morris Inc., the Dayton Hudson Foundation and the National Endowment for the Arts to stage an exhibition of new Western art. The Corcoran's Clair List traveled West to find it.

There are hundreds of good artists in California. Wet Washington and sunny Texas don't have much in common. This Western show, no doubt, tells us just as much about Clair List's preferences as it does about that region's modern art.

List, a Baltimorean, writes that she was taken by "the underlying spirit of quirkiness, comic vivacity and authentic gusto" that she found "out West." She has tried, she adds, "to emphasize the differences between East and West. I wanted to highlight the welcoming, unhesitating and sometimes eccentric spirit of Western artists."

Most of the art she's picked, perhaps not surprisingly, grabs the viewer quickly and fulfills its mission briskly. A spirit eager and impatient stalks this exhibition.

Joe Baker's canvases, for example, although nicely painted, do little more than satirize the Indian pictures of Fritz Scholder. Scholder puts eagle-feather headdresses on noble Indian chiefs. Baker, instead, places them on women wearing bathing suits and shopping-center shoes, or on the heads of dogs.

Ed Blackburn copies stills from '40s cowboy movies. We get his art at once. The same holds for Margaret Nielsen's, which shows assorted objects--a telephone, a cupcake--hurtling through the air. The carefully made bitter jokes of Masami Teraoka take a little longer. His style is the style of the woodblock prints of old Japan, but he slips into his pictures Sonys and bikinis, the Kleenex and the beer cans of Hawaii, where he lives. Robert Colescott boldly paints a black-skinned Shirley Temple making eyes at a white-skinned Bill Robinson. Such modest one-shot witticisms appear throughout this show.

There is a fear of slowness here. New Mexico's John Fincher, whose handsome little still lifes owe much to Wayne Thiebaud's and also to Jim Dine's, undercuts his seriousness with his subject: shaving brushes. Dan Rizzie's elegant abstractions so immediately recall the cubist art of Braque, and that of the constructivists, that it, too, feels familiar. Its messages are messages we've received before.

The most impressive painters here are those who hold a little back. Peter Alexander's gorgeous abstractions done on velvet cannot be easily, or entirely, deciphered. Vernon Fisher's word-filled pictures, too, retain a quality of mystery. Ron Hoover's are yet stranger. Looking at the ghosts and flags and clothes hangers behind his sprinkled surfaces is like visiting a dream.

Gaylen Hansen's dreams have comparable authority. His colors are fine, and though he has learned much from the simplicities of folk art, as have others in this show, his art will not stay simple. Nor will that of Michael C. McMillen, who counters in his work the sunniness that marks this exhibition. McMillen paints small sinister interiors whose cartridge cases and battered surfaces suggest the dark side of Southern California, which Philip Marlowe stalked.

There are so many jokes, quick hits and references to familiar older art in this exhibition, that Theodore J. Waddell's cattle paintings somehow seem quite special. Dark animals, not clearly seen, breathe softly in the darkness, and become part of the landscape. Waddell, a Molt, Mont., cattle rancher, offers us the opposite of flashy, glitzy art.

The modern West, of course, like the West's modern art, is a blend of many things, of the movies and the mountains, of privacy and show biz, and, as this show makes clear, of art learned from the Orient and from Europe and from the magazines. Many of the objects here suggest a pedigree that's mixed. The little elegant abstractions of James Hueter suggest, in their loyalty to symmetry, the hard-edge California art of, say, John McLaughlin, while honoring simultaneously the lessons of the abstract expressionists and California's potters. It is also odd to see here the way the half-erased blackboard look of Cy Twombly and conceptualism has infiltrated, say, a dozen pictures in this show.

Its energy is palpable. Its worst art isn't all that bad. It may, or may not, accurately survey the new art of the West. But it does have worth. Painters struggling in this city should be glad to see others, no better, no more famous, receive the exposure granted by such a traveling show. It will go to Peoria, Scottsdale, Albuquerque, Long Beach, Laguna Beach and San Francisco, after closing here April 3.