A CERTAIN AMOUNT of tension inevitably builds up around art works that exist on the edges of definition. Martin Puryear's solo exhibition at the McIntosh/Drysdale Gallery demonstrats this. Made up entirely of large wooden pieces that hang on the wall, each a variation on the theme of the circle, the show is at once calming and unsettling.Part sculpture, part painting, part craft, Puryear's work fits no simple niche. It touches directly upon Brancusi and 1960s minimalism and, in a general way, upon non-European ceremonial art. But its intensity derives less from resisting this sort of classification than from certain built-in contraries that somehow do not cancel each other out: the forms are rational, obdurate and cold, but the painted, stained and rubbed surfaces are sensuous and beautiful; the shapes are simple and basic, but no two are alike; the pieces suggest perfection, but deny it in subtle irregularities.

"Azul-Azul," for instance, is a not- quite perfect circle of wood about 2 inches thick and5 feet in diameter, an elementary form that lights up the wall with its flecked surface of blues and greens. It reminds me a lot of those "Unfurled" paintings by Morris Louis, which likewise defined an empty central space with color. "Rapprochement," on the other hand, is a dark arc that almost becomes a full circle. The way the surface is rubbed portends some ancient, ritual use and yet the two almost touching tips also suggest Michelangelo's moment of creation on the Sistine Chapel ceiling.

Puryear, born in Washington, now works in Chicago. His stubborn attention to the hard lessons of the woodworker's craft dates back to sojourns in Africa and Sweden in the 1960s. One is always conscious of his ability to make wood do what it doesn't want to do. This, too, contributes to the strange persuasiveness of his art. Through March 3 at 406 7th St. NW. The gallery is open Tuesdays through Saturdays, 11 a.m. to 5:30 p.m. Latin Mystery

A pervasive mysteriousness unites the exhibition, "New Painting of Costa Rica," on view at the Organization of American States. Otherwise, the show of works by 13 painters is a study in provincial diversity, touching numerous European modernist bases.

Jose' Gomez Sicre, director of the Museum of Modern Art of Latin America, observes that, until recently, paintings in Costa Rica have focused almost exclusively on the local landscape and scenes of rural life. In this show, the naive works of Amparo Rivera alone fit that description, but even Rivera's head-on descriptions of Costa Rican buildings are unpeopled and quite strange in effect.

Other painters such as Xenia Gordiano and Rodolfo Stanley give local still life or figurative subjects ominous, surreal overtones. Collage paintings by Lola Fernandez do something of the same thing with the subject of political violence, with bloody images shrouded in a maze of gaskets and machine parts. Even Alberto Ycaza's elegant, luminous geometric abstractions, containing plumb bobs and pendulums, define a darkly beautiful sort of uncertainty. Through March 6 at 17th Street and Constitution Avenue NW, open 9 a.m. to 5 p.m. Mondays through Fridays. Reginald Pollack

Reginald Pollack's paintings occupy both large floors at the Jack Rasmussen Gallery. This is a mixed blessing because Pollack's virtuoso, gestural oil paintings of swirls of angelic-demonic figures cavorting in brilliant, sometimes lurid colors upon plastic-coated Masonite panels can be numbingly repetitive. But the virtue of such a full showing is that ironically it brings home the lesson of Pollack's idiosyncratic art. His is an ecstatic, religious vision pursued with a rich, cumpulsive energy. Good taste plays no part in it. Through March 6 at 313 G St. NW, from noon to 5 p.m. Tuesdays through Saturdays. New Painter at Foundry - Deborah Brown is a young (age 26, two years out of graduate school) painter whose first solo exhibition at the Foundry Gallery is predictably tentative and unpredictably fresh. Brown's approach involves a swashbuckling sort of brushiness held in check, at her best, by intense color modulations and solid structure. The paintings in the show describe tennis matches at the Rose Park courts in Georgetown. Everything comes together in fine fashion in tense, luminous paintings such as "Rose Park," Nos.4, 7 and 8. Through March 6 at 641 Indiana Ave. NW, open Tuesdays through Saturdays from 11 a.m. to 5 p.m.