Rod Evans says there's plenty for a guy in his 30s to like about a retirement community. No loud stereos, no rowdy parties down the hall, no crowds in the fitness room.

Though the 39-year-old steers clear of the mah-jongg tournaments downstairs, he says he has plenty of friends on the top floor of the Biscaya Four condominiums in Aventura. But the building elders don't want him to buy a unit, citing bylaws requiring owners be 55 or older.

''I do feel discriminated against because of my age,'' said Evans, a waiter who rents a Biscaya condo with his girlfriend, Daphne Quiquin. He has lived there since 1994, two years before the condo association adopted a 55-and-over ownership restriction for the eight-story building overlooking the Turnberry Isle golf course.

Evans is pushing to buy into one of South Florida's many seniors-only buildings just as the dynamics of retiree marketing are pushing them out of favor. While aging home buyers once flocked to communities reserved for retirees, developers say the new generation of retirees wince at the senior citizen label.

''How many shuffleboard courts do you see being built today?'' asked Bradley Hunter, a housing analyst for American Metro Study Corp. ``Anything that has a stigma to it -- as far as being old and as far as being retired -- I think will be a negative for them.''

With the number of Americans older than 64 predicted to double within three decades to 70 million, retirement communities are a leading housing trend.

While age-restricted communities will remain popular, some experts predict developers will increasingly favor projects designed for retirees without broadcasting age as the top criteria.

''Baby boomers . . . are going to be the biggest retirement market we've ever had,'' said Lewis Goodkin, president of Goodkin Consulting in Miami. ``That audience is very sensitive to age.''

Such sensitivity is not a problem for Evans, who said he doesn't mind the generation gap with his neighbors. Though he said he isn't the youngest resident there -- federal law allows communities like Biscaya to exempt up to 20 percent of its units from age restrictions -- most of the people he sees are old enough to be his parents.

The Biscaya rules are based on a 1988 change in the national Fair Housing Act outlawing discrimination against families. Buildings had routinely barred children as residents, but the new law ended that while carving out an exemption for elderly housing.

Communities could restrict themselves to seniors, provided at least 80 percent of their residents were older than 54.

After adopting the restriction, Biscaya agreed to honor Evans's lease for as long as he wanted to stay. But the building's lawyer says letting him buy the unit would make it impossible to turn other young people away.

''If you don't follow the rules to the letter, you lose your ability to enforce the rules,'' said Lisa Magill of Becker & Poliakoff in Fort Lauderdale.

Victor Schaffzin, 90, voted for Biscaya's age limits, but now he's having second thoughts.

Schaffzin thinks the rules are hurting resale values by limiting potential buyers, and he said he particularly doesn't like the idea of shutting out that ''nice, young man'' on the eighth floor. After all, it was Evans who put together Schaffzin's computer.

''He's been here for so many years,'' Schaffzin said. ``He's friendly and helpful in every which way.''