Even before it officially convenes, International Sculpture '90, the five-day conclave of a thousand sculptors opening here tonight, seems to reflect the 1990 art world in microcosm. Cut back, scaled down and more concerned with numbers than with the new, it is deeply worried about artistic freedom and the environment. It is also busily exploring new possibilities abroad, especially in Japan.

These concerns are evident in the rich mix of overlapping panel discussions, lectures and exhibitions organized by the Washington-based International Sculpture Center, a 30-year-old nonprofit service organization for sculptors and sculpture-related activities working out of a rented town house in Georgetown. International Sculpture '90 gets underway tonight at 8 at Lisner Auditorium with a keynote speech by National Endowment for the Arts Chairman John Frohnmayer, to be followed by a short address by former representative John Buchanan, chairman of People for the American Way.

Issues of government funding and censorship seem to haunt the program, and will be the subject of several panel discussions set for tomorrow. Other topics through Saturday cover the gamut from technical matters, such as pricing and how to build a foundry, to aesthetic concerns, such as "Art as Architectural Band-Aid," featuring artists Alice Aycock and George Sugarman, and "Collaboration: Too Many Cooks?," in which artist Nancy Holt and others will discuss the possible pitfalls of the increasing collaborations among artists, developers and architects.

Several well-known artists will talk about their work, among them Vito Acconci, Dani Karavan and Christo, who will discuss his latest endeavor, "The Umbrellas Joint Project for Japan and USA." Japanese art critic and curator Fumio Nanjo of the Institute of Contemporary Arts in Nagoya and Junichi Shioda of Tokyo's Setagaya Art Museum will talk on contemporary sculpture in Japan. Curators and critics from France, Latin America and Ireland will also discuss recent trends and activities.

Though only registrants will be admitted to these events (registration is $235), there are also 64 sculpture exhibitions of every sort in various galleries, cultural centers and museums around town, many prompted by the conference.

ISC last surfaced here a decade ago with the 11th International Sculpture Conference, an event that left behind happy memories of Rockne Krebs's laser light levitating over the Mall, along with J. Seward Johnson's cast-aluminum giant, who still struggles to unearth himself on Hains Point.

Between 1960 and 1982, the ISC held sculpture conferences in various cities every other year, until financial crisis hit after its sole patron -- the aforementioned sculptor and Band-Aid heir Johnson -- pulled out in the wake of a court battle over his father's estate. Since then, with the help of a strong new board of trustees and after netting more than $400,000 at a Sotheby's auction last September of works donated by member sculptors, ISC cleared its debt with money to spare.

International Sculpture '90, given the go-ahead only after the success of last fall's auction, is the first international sculpture conference to take place in eight years. In major respects, however, it is not the "reincarnation" of the 1980 conference that ISC Executive Director David M. Furchgott had originally expected.

"We got some very good support, but not as much as we'd hoped," admits Furchgott. For one thing, the projected $650,000 budget turned out to be a pipe dream, and with only a third of the expected 3,000 advance registrants, the fiscally responsible board cut back drastically on outdoor installations. The result: Instead of the 88 ambitious outdoor works seen here in 1980, there are only five, most of them along Pennsylvania Avenue, most relatively modest in scale and none site-specific. Only two were installed by early yesterday -- a sheet metal cocoon filled with broken furniture by Kimio Tsuchiya near the Corcoran, and a quiet, contemplative wood piece by Shigeo Toya on the grassy area near the National Archives. Still in progress was an installation by Venezuelan artist Rolando Pena of 28 oil drums painted gold on a triangular island in front of the National Gallery West Building. The works by Viola Frey (at 1201 Pennsylvania Ave. NW) and Allan McCollum (1001 Pennsylvania Ave. NW) were due to be installed by today. A single work by Giancarlo Neri, originally meant to go outside, has found a home in the Georgetown Markethouse, at M and Potomac streets NW. The used-furniture installation can be viewed through a window.

"If we'd gotten a million dollars to do outdoor installations, we'd have dotted the city with them," says Furchgott.

"One major disappointment is that the rules have changed a bit regarding the placement of public sculpture on a temporary basis," he says. "Now the National Park Service has a standing rule that displays of works of art can only get a three-week license, and the cost of bringing them in is too high for that. Almost every green spot on view downtown is under the Park Service, and though -- within that context -- they've been cooperative, there'd be little or nothing downtown if it hadn't been for the Pennsylvania Avenue Development Corp.

"The Kennedy Center was also a major disappointment," says Furchgott, who expected to place several major indoor sculptures there, until he was informed -- last week -- that it too falls under the Park Service time limit of three weeks.

Working fast, Furchgott struck a deal with the owner of the building at 406 Seventh St. NW, where all but one of those works (the Louise Bourgeois sculpture was too heavy) had to be hauled up to the third floor and installed. Without funds to pay the unexpected rental, Furchgott swapped a donated Isaac Witkin sculpture for the space, and was given a last-minute grant from the Glen Eagles Foundation to pay for gallery sitters. His back, meanwhile, is in a state of torment.

Large installations by Houston Conwill, Willie Cole (constructed from 120 hair dryers) and Mierle Ukeles, an artist in residence with the New York Department of Sanitation, will be included in this promising group at 406. So is Steve Barry's intriguing "I.D.," a photo booth of sorts in which you sit before a panoramic desert scene, push a button and disappear. It is but one of several works around town meant to remind us that we're part of a natural universe, and had better pay attention. Barbara Kornblatt's Mel Chin installation (downstairs) deals with similar issues.

Such works make clear how dramatically sculpture has changed since the ISC began in 1960 as the National Bronze Casting Conference, the idea of one professor at the University of Kansas Sculpture Research Center, Elden C. Tefft, who wanted to assist other sculptors in getting their work cast at a time when foundries in America were rare. He is a participant this year as well.

ISC has also changed dramatically since 1979, when David Furchgott, a 32-year-old arts administrator from Charleston, S.C., was hired by Johnson, then chairman of a board that consisted entirely of his family and business associates. The previous year, Johnson had agreed to take over from Tefft and to set up the International Sculpture Center in Washington as a tax-free, nonprofit organization. By the time of the next conference in Oakland in 1982, ISC had become an organization with 2,000 dues-paying members. It had also started the respected magazine Sculpture, and established group health and studio insurance programs for artists, as well as discount foundry and supply programs.

Today, it has more than 10,000 members in 71 countries. It also organizes income-producing traveling sculpture exhibitions for museums abroad -- particularly in Japan (a Frank Lloyd Wright retrospective is next) -- and maintains the world's most advanced computerized file on sculptors, serving as go-between for potential clients seeking artists for commissions. "When a group wanted an Afro-American sculptor to do a portrait of the first president of Botswana, we realized we needed a more objective way of finding artists than just calling up curators on the phone," says Furchgott.

The only thing really lost by the diminished outdoor component of International Sculpture '90 is the overview it might have offered the public of what's in store for the '90s. "We had asked 12 leading curators from all over the world to list the artists they thought would be of consequence, or continue to be of consequence in the '90s, and came up with a wish list of 71."

Only a dozen of them will actually be exhibited in the shrunken ISC selection on Pennsylvania Avenue and at 406, though others will be discussed by various curators in the panel sessions. In any case, the list will be published later this week, and will doubtless be a hot item among dealers and collectors who care about such things. Unfortunately, it's in alphabetical order, and all Furchgott would say about the Top 10 is that video artist Bill Viola is among them and Jeff Koons is not.

Furchgott, who calls himself "a specialist in short-term projects," remains upbeat about the future, and hopes International Sculpture '90 will be successful enough to warrant periodic conferences in the future, preferably every three to five years, and preferably in Washington. "We'll have to wait and see," he says.

But as he walks across Pennsylvania Avenue to take a look at Toya's "Death of the Forest" near the National Archives, which he helped install, he is pleased to see two women carefully inspecting its seemingly scorched, scarred interior.

"They're carrying Corcoran bags, so they must be art lovers," says Furchgott. "That makes me happy. I'm doin' my job." Registration for International Sculpture '90 is open to all, and will take place today between 3 and 7 p.m. at Lisner Auditorium, George Washington University, 730 21st St. NW, ISC headquarters during the conference. For information call 965-6066.