The Supreme Court set off a major trademark controversy yesterday by permitting Parker Brothers to be stripped of its 48-year-old monopoly on use of the name Monopoly for its famous real estate board game.

Without comment, the justices let stand a ruling invalidating the Monopoly trademark because the term has become generic--that is, a common descriptive name for that type of board game.

Critics say the ruling endangers trademark protection for hundreds of brand-name products from soaps to video games. Trademarks that have invalidated in the past because the names fell into common use include those for aspirin, cellophane, cola, thermos and yo-yo.

Monopoly was patented in 1933 by Charles Darrow, an out-of-work heating engineer who borrowed street names from Atlantic City, N.J., for his game board. Parker Brothers acquired a trademark on Monopoly in 1936, and the game's success--more than 80 million sets sold to date--made Darrow a millionaire before he died in 1967.

In 1973, marketing began for a game called Anti-Monopoly. And Parker Brothers soon warned its inventor, San Francisco State University economics professor Ralph Anspach, that it considered his game's name an infringement on its trademark. Anspach went into federal court to have the trademark declared invalid.

U.S. District Judge Spencer Williams of San Jose, Calif., twice ruled for Parker Brothers, but the 9th U.S. Circuit Court of Appeals twice reversed him, announcing its latest ruling last Aug. 26.

Under trademark law, a registered trademark loses its legal protection when it becomes generic--a "common descriptive name." The 9th Circuit court interpreted the test to mean "that, when a trademark primarily denotes a product, not the product's producer, the trademark is lost."

The panel based its ruling in part on a marketing survey that showed most consumers were motiviated to buy Monopoly because they were interested in the game and did not care who manufactured it. "When a trademark primarily denotes a product, not the product's producer, the trademark is lost," the court said.

In seeking Supreme Court review, Parker Brothers contended that such an interpretation of trademark law could have a devastating economic impact.

"Actual or potential competitors of many highly successful products that have become publicly identified by their brand names may henceforth pirate such brand names for their own use with impunity," the justices were told.

The appeals court ruling also was attacked in friend-of-the-court briefs submitted by the Grocery Manufacturers of America, the National Association of Manufacturers, the Chamber of Commerce of the United States, the Toy Manufacturers of America and the U.S. Trademark Association, an organization of trademark owners.

Monopoly "is the nearest word or term which would be used to describe a game of such type and would be needed by anyone who wanted to market such a game," the Anti-Monopoly attorneys said.