YOU'RE NOT going to slap your thighs in "Metropolitan." Nor should you indulge in such low-class behavior. Whit Stillman's modern comedy of manners is designed for urbane smirks, polished titters and other forms of sophisticated drollery.

Set among the upper prep set of New York, where you are what you are invited to, the humor is frequently lobbed so high it's liable to float right over your head. Made about and for the so-called upper haute bourgeois (or UHB, phrase coiners), "Metropolitan" doesn't take the predictable tack of twitting the leisured, so much as ironically mourning their passing.

The story revolves around a small gathering of young Park Avenue socialities who call themselves the Sally Fowler Rat Pack, after one of their own. It's debutante season, time to flit from gowned party to party, discuss 19th-century social reformer Charles Fourier, do the cha-cha and even indulge in a little drawing-room strip poker.

But there's a problem this time around: a distinct lack of male escorts. This prompts the clique to allow social outsider Tom (Edward Clements) to enter into their midst. He immediately becomes the escort for Audrey (Carolyn Farina), who takes a more than strong liking to him. Tom, it turns out, not only has definite, non-UHB opinions of his own, he's still hung up on an old girlfriend (Elizabeth Thompson). A clash of hearts and manners is inevitable.

There is something tragic and tender between the lines of this otherwise not exactly hysterical comedy. Stillman certainly has captured a world we don't see too often. It's also nicely ironic that this movie about the highfalutin was done on a shoestring -- the characters are often seen walking out of the Plaza Hotel, but are never filmed inside it.

But in his microcosmic zeal to identify this world, Stillman leaves "Metropolitan" a one-joke movie. Rather than transcend his narrow frame of reference, Stillman keeps his characters doing little more than exchanging witty repartee. Tom's dramatic "invasion," which results in a tritely drawn boy-meets-girl combination, does little to stir things up for the movie. Stillman's social backdrop becomes the main attraction -- by default.

Obviously lacking the correct social graces needed to fully understand this film (I tend to dunk doughnuts in my coffee and eat with my elbows on the table), I found myself watching "Metropolitan" with a sense of being left out and did not laugh more than once or twice. I suspect, as with Spike Lee's "School Daze," true appreciation for this movie may be restricted to those with firsthand experience in this kind of world, or a certain upper-haute stamina.