BY THE ADMISSION of the National Museum of African Art's director even, "A Concrete Vision: Oshogbo Art in the 1960s" is not a full-blown exhibition. Rather, Roslyn Walker calls it an "introduction" to the pioneering early days of an art movement that sprang up in the western Nigerian town of Oshogbo.

Centered around four whimsical concrete screens by Adebisi Akanji, the group show of 11 Oshogbo artists is also meant to be taken as a hint to donors and lenders that the museum would like more items in its collection from this underrepresented period and place. The reinforced concrete screens, a latticework depiction of everyday life (figures pump gas, play music and bicycle about town), were donated to the museum in 1994 by collector Waldemar A. Nielsen and his wife, who commissioned them in 1966. Much of the rest of the show was lent from three local collectors.

After sitting in the elements of the Nielsens' Manhattan garden for a quarter century, Akanji's screens were badly damaged. Heat, cold and moisture, seeping through the barely two-inch-thick concrete, caused the armature supporting the cookie-cutter-like shapes to corrode, in some cases causing the steel rebars inside to expand to three times their size and break through the fragile shell. It's no exaggeration to say that when the African Art Museum acquired the sculptures they were falling apart.

So in addition to what Walker calls the "contextualizing" of the centerpiece--what were Akanji's artistic contemporaries doing when he made these unorthodox works?--there's a conservation component to this show as well. Much of the time since the acquisition of the screens has been spent researching and treating the screens in order to stabilize and preserve them. Complicating this endeavor, according to conservator Dana Moffett, was the fact that the now elderly artist speaks no English and when tracked down at home was able to provide little useful information about their construction and composition. Moffett says that a similar installation of concrete screens fabricated for an Esso gas station in Oshogbo (depicted in the exhibition only in a photograph) is reputed to have been stolen overnight many years ago.

Back to context: Many of the early Oshogbo artists came out of a theater troupe run in the 1960s by Duro Ladipo, soon to become a well-known playwright and producer. In addition to being actors, musicians, set designers and costumers, several of Ladipo's company members took a series of visual art workshops run by such expatriates as American Jacob Lawrence, German Ulli Beier, Englishwoman Georgina Beier and Austrian Susanne Wenger (the last two are represented in the show with a handful of their own works). It was not only during these classes but during international tours with the theater that the Oshogbo artists gained exposure to modern techniques and styles. Soon, they were leaving behind such traditional subject matter as religion to explore the realm of pure imagination. Several of the artists, most of whom were Yoruba, had begun by reinterpreting tribal myths.

Much of the work, like Akanji's screens, consists of simple, graphic patterns. Some is swirling surrealism, some bold abstraction, some cartoonish figuration. Some is in the warm, molten hues of the African countryside, but just as often the artists resort to basic black and white. Some is in carved stone, some in oil on wood, some in artsy-crafty yarn and beads glued to boards and some in hammered aluminum.

Perhaps the best-known and most intriguing of the 11 artists is a man named Twins Seven-Seven, so-called because he is the only surviving member of seven sets of twins born to his mother. Also an accomplished musician (you can sample two of his Afro-pop recordings at listening stations), Seven-Seven today devotes most of his time and energy to politics, although his intricate and fantastical drawings and one painting from the '60s and early '70s (with such elaborate and spectral names as "The Lazy Hunters, and the Poisonous Wrestlers, Lizard, Ghost and the Cobra") are among the show's most powerful and poetic work.

If "A Concrete Vision" frustrates, it is only because the overall strength of the work makes you yearn for even more context. The show may be limited chronologically and geographically, but not aesthetically.

As curator Andrea Nicolls puts it, the Oshogbo art of a single early decade "does and doesn't fit into tradition." Yet exactly how, exactly what came before and what ultimately grew out of this isolated cultural explosion is not answered. That, I suppose, is the subject of yet another exhibition that may still be languishing in some aesthete's garden or attic. I join the curatorial and conservatorial staffs of the National Museum of African Art in wishing that all such pack rats out there might take the hint.

A CONCRETE VISION: OSHOGBO ART IN THE 1960s -- Through Oct. 22 at the National Museum of African Art, 950 Independence Ave. SW (Metro: Smithsonian). 202/357-2700 (TDD: 357-1729). Web site: www.si.edu/nmafa. Open 10 to 5:30 daily. Free.

Public programs associated with the exhibition include:

Saturday at 1 -- Documentary film: "The Oshogbo Artists."

Saturday at 2 -- Lecture: "Reminiscing about an African Renaissance: Oshogbo in the 1970s."

Sunday at 2 -- Gallery discussion: "Another View: 'A Concrete Vision: Oshogbo Art in the 1960s.' "

Feb. 19 at 1 -- Documentary film: "The Oshogbo Artists."

Feb. 19 at 2 -- Lecture: "Oshogbo Art in Retrospect."

Feb. 26 from 2 to 4 -- Art workshop for children ages 7 to 13: "Pressed into Foil."

Excerpts from the film "The Oshogbo Artists" and from the recordings of Twins Seven-Seven play continuously in the gallery.