(FORTUNE Magazine) – Male chauvinists might think the Supreme Court's ruling that many men's clubs must admit women rings clubdom's death knell. But a look at clubs that have gone coed voluntarily suggests quite the opposite: Once the dust of coed conversion settles, membership, revenue, and use often increase. Marc Onigman, publisher of Club Industry, a magazine for those who operate clubs, says, ''Managers know they'll do more business once clubs open up. Imagine if McDonald's catered only to men.'' Adds Fred Shaner, manager of Chicago's once all-male University Club: ''Theoretically you could say we've doubled our market.'' Coed clubs' vigor stands out against the less-than-chipper face of clubdom generally. Surveys by Pannell Kerr Forster, the accounting firm that audits the books for around 300 U.S. clubs, show membership in city clubs either stagnating or in decline everywhere except the Far West. In the greater New York City area, more than a third of institutions responding said membership since 1970 had declined. ''We're better off,'' says A. Scott Ritchie, president of the Wichita Club in Kansas, which has been admitting women since 1975. ''Without them, we'd have financial problems. Because they're young, they use the club a lot.'' What's more, he notes, ''they're attractive, they tend to dress up the dining room.'' His advice to clubs fighting to stay all male: ''Don't.'' Clubs with aging memberships find going coed helps attract younger applicants. Young clubmen, fearing the social stigma of elitism, became practically an endangered species in the 1960s and early 1970s. Now they are being seen again. Jack B. Quick, manager of the University Club in Washington, D.C., says that while his club's overall membership is up 5%, membership of the 21 to 30 crowd is up 10% since 1984, the year the club went coed.