Joseph Hirshhorn thinks that David Smith is the "most important sculptor America has produced so far. I feel it in my gut, my heart, my brain."

As usual, Hirshhorn has backed his instincts with acquistitions. As a result, 32 works by David Smith (190665) -- all now part of the Hirshhorn Museum's own collection -- go on view there today.

The show is one of an ongoing series devoted to exploring artists whose work the museum holds in depth. Though by no means a fullblown retrospective (the show fills only two galleries and a connecting corridor), it spans Smith's career from 1946 to the late, great "Voltri" and "Cubi" series completed just before his death.

Hirshhorn is hardly Smith's only fan. He is now generally considered a breakthrough figure in mid-20th-century art, especially for the new sculptural vocabulary he devised at a time when many artists had returned to molding clay and carving wood.

Inspired by the "assemblage" idea of the cubists, notably Picasso, Smith began making three-dimensional assemblages of "found" metal objects and shapes in the '40s, all welded together into vital and highly expressive forms which exist on the taut boundary between figuration and abstraction.

He also inspired a whole generation of artists to create "drawings in space" -- from the formalist Anthony Caro to the romantic Mark di Suvero -- and, less hapoily, to make Junk" sclupture, much of which fits the description.

Those familiar only with Smith's late work (the "Voltri" series was featured in a spectacular installation at the National Gallery East's inaugural show), will find the wealth of small, early sculpture and painting fascinating.

Hirshhorn's earliest purchases in 1946 included three in a series of 15 bronze plaques dealing variously with what Smith called "the dishonor of our time" -- the rise of the Nazi regime.

One biting example, which at first appears to be an array of Greek coins, is called "War Exempt Sons of the Rich," in which polo-playing playboys tilt at windmills while others are gassed. In "Elements Which Cause Prostitution," an innocent helmetshape turns out to be filled with syringes, pockmarked surface and references to abortion and disease. This is not the David Smith most audiences are familiar with.

Among the works (annoyingly arranged without chronological order) are fine examples from most of Smith's major themes. He liked to work in series and in several different styles at once, and that is clear here, though tracking down which happened when is difficult.

Also clear are the great vitality and fecundity of Smith's sculptural imagination. Their pervading classicism is surprising, given the very avant-garde look of his work less than a decade ago. Much has happened in sculpture since Smith died, and much of it because of him.

Other surprises included three paintings, chiefly of scholarly interest, which reveal that Smith continued to work in this medium even after switching his major efforts to sculpture in the '30s. Most interesting is a large painting from 1958, 'White Egg with Pink," made by setting out cut metal or cardboard shapes on white canvas and spraying around the edges with metallic paint, leaving a negative image, Smith often constructed his sculptures thus, by setting them out on white rectangular areas painted on his floor or worktable.

Smith spent a lot of time talking about the importance of color in sculpture, but the least interesting example in this show is "Albany IX," which is paintedin various colors. The color that really matters in his work is in the great variety of patinas and surfaces, from the pale blue of "Auburn Queen" to the light-reflecting "Cubi XII," where dalligraphies of light seem to hover just behind the surfaces.

In 1962, Smith created 28 sculptures in 30 days for the Spoleto Festival, and the Hirshhorn owns five examples from this "Voltri" series, purcahsed just after the artist's death. "I'm sorry I didn't buy more," says Joe Hirshhorn today. "They actually brought two different wagons out to my place in Greenwich, and I sent them back. I must have been in a bad mood."

But the Hirshhorn now owns the largest collection of Smith's work now in a public museum.

The show continues through Oct. 28. A fully illustrated catalogue by Hirshhorn curator Miranda McClintic is available. CAPTION: Picture, One of David Smith's "Drawings in Space"