June 29, 1981

The Hilton Hotel in New York is losing 25 percent of its foreign clientele to cancellations. Worse, at the city's five Sheraton hotels, three out of four overseas tour-group reservations are noshows - twice as many as last year. And Thomas Cook & Sons, the British travel agency, notes a ''significant dropping-off'' of overseas tours to the United States. Why the cold shoulder? The reasons are purely economic, says Jorgen Hansen, Hilton's general manager. ''The exchange rates have gone out of sight for some of these people,'' making foreign travel much more expensive, he said.

Twelve years ago yesterday Morty Manford was 18 years old and a patron in the Stonewall Inn, a homosexual bar in Greenwich Village, when the police raided it in the early morning, setting off a riot by 300 young men in which 13 were arrested and four police officers injured. It marked the beginning of the homosexual rights movement. Yesterday, Mr. Manford, a third-year student at the Benjamin N. Cardozo School of Law at Yeshiva University, walked shirtless up the middle of Fifth Avenue with his mother, Jeanne, and tens of thousands of other homosexual men and women, some of their parents and some of their friends.

The awards ceremonies of the Moscow open chess championship today followed the usual pattern of congratulatory speeches, inside jokes and handshakes until the winner, Boris Gulko, asked to speak. An expectant hush fell over the officials and participants gathered in the ornate main hall of the Central Chess Club. It was common knowledge that Mr. Gulko, an international grandmaster and the Soviet champion in 1977, had not played in a major tournament since he and his wife applied to go to Israel in December 1978. Speaking nervously and rapidly, Mr. Gulko declared that he had written an open letter to the Soviet Chess Federation insisting that it take action to permit the emigration of the wife and son of Viktor Korchnoi, the defector who is scheduled to make his second bid in the fall to wrest the world chess crown from Anatoly Karpov of the Soviet Union.

Seated comfortably in his downtown office, looking out over Governors Island, Brooklyn and the East River, A. Robert Towbin grimaced at the mention of the thriving market for new issues. ''There's a thing about new issues that has a ephemeral quality,'' said Mr. Towbin, senior partner at L.F. Rothschild, Unterberg, Towbin. ''But we're here for the long run. ''You don't look at Rothschild just for new issues -you look at us for creative investment ideas.''

Two steel cables on the Brooklyn Bridge snapped last evening, severely injuring a pedestrian and causing the bridge to be closed for more than three hours. After the accident, which did not involve any of the strands supporting the weight of the roadway, traffic backed up on the Manhattan and Brooklyn sides until engineers assessed the damage. Cars were permitted across again at about 9:15 P.M., but pedestrians will continue to be barred until the damaged walkway is repaired. Leon Mandel of Manhattan was walking across the bridge from Brooklyn when the accident occurred at 5:50 P.M., near one of the towers on the Manhattan end.