Information about Eastern European artists will be easier to obtain now, thanks largely to the efforts of Czech-born art historian Mada Mladek, now a Washingtonian. Mladek, who has promoted the cause of Czech artists for many years, has lobbied successfully to establish information centers on this group of artists, long isolated from the international art world.

"I realized why this is such a difficulty . . . why this country seems culturally forgotten. Curators did not know where to go to look for Eastern European artists," says Mladek of the problems westerners encounter trying to locate artists from Hungary and other Eastern European countries.

The centers -- called documentation centers -- have been opened simultaneously in Budapest and the National Gallery of Art. They'll provide information for American curators and art collectors, thus opening possibilities for Eastern Bloc artists here and on the international art circuit.

Mladek persuaded a number of art world officials to be on the centers' advisory committee. Guggenheim Museum Director Thomas Messer is the committee chairman. Also on the board are J. Carter Brown, executive director of the National Gallery; Michael Compton, director of London's Tate Gallery; and Dieter Ronte, director of Vienna's Museum of Modern Art. Five members of the Hungarian Academy of Sciences' art department also sit on the committee. The project is partly funded by the Hungarian government and by New York businessman George Soros -- a Hungarian American.

The American documentation center is located in the National Gallery's Center for Advanced Studies in the Visual Arts, which is directed by Hank Millon. Millon also will be responsible for administering the Documentation Center. The Center for Advanced Studies awards research fellowships to art historians and those in related fields.

Millon says that all documentation on the artists will be listed in the gallery's library, and photographic documentation, such as slides and pictures, will be on file in its photographic archives. A copy of all the documents with the National Gallery will be on file at the documentation center in Hungary. 'Show Boat' Concert Delayed

That special week of music to be performed Jan. 7-12 by the renamed Kennedy Center Orchestra has been postponed to an undetermined date. The problem, it seems, is that the orchestration of those rarely heard tunes from the musical "Show Boat" is taking longer than expected. For more information, call 254-3770. Hull Gallery Closing

After eight years in business, the Hull Gallery, 3301 New Mexico Ave. NW, two blocks from American University, is closing tomorrow. Anne Hull, who has made a reputation for herself with monthly shows of contemporary Washington artists, has decided to retire from the gallery business. "[Hull] has had the gallery for eight years, happily and successfully, and she's been very proud to show a number of contemporary artists," says Assistant Gallery Director Beatrice Goldberg.

The Hull Gallery also put on an annual show of well-known artists from its inventory, which included Sanford Gifford, Thomas Hart Benton, Reginald Marsh and other American artists. Most of those works have gone to auction houses here and in New York City.

Carlton Fletcher and Lee Newman, who have exhibited with Hull for the last three years, have turned around and opened their own gallery -- Circle Gallery, at 3232 P St. NW -- and a school -- the Washington Studio School -- upstairs.

"Each is supposed to serve the other . . . the school will use the gallery as a teaching tool," explains Fletcher, who is president of both school and gallery. Fletcher says the school will offer nondegree courses in drawing, painting and printmaking for all skill levels.

The school/gallery is something of a class reunion for the faculty -- Fletcher, Newman, Jack Boul, David Holt, Katy Murray, Joseph Kossow and Susan Yanero -- all of whom met while pursuing art degrees at American University. The first show, which opened Dec. 1, features their work. Not surprisingly, the next show, beginning Jan. 20, will exhibit the work of a former chairman of the American University art department, Robert D'Arista.

Georgetown is a costly place to start a school cum gallery these days and is geographically distant from many Washington arts organizations, but Fletcher comfortably acknowledges the risk. "The gamble is that we can pay a Georgetown rent, put ourselves in the middle of the Georgetown bustle and see if people are drawn to us.

"We want to cover a slightly different area that is not so avant-garde . . . somebody has to handle the basics of how art makes meaning," says Fletcher. "We don't want to stake out the same area that somebody else has, but we feel there's a gap."

The gallery is open 11 a.m. to 4 p.m. Tuesday through Saturday. For information about the school or gallery, call 333-2663.