"THE PHILADELPHIA Story" operates on the premise that "there's not a prettier sight in this whole civilized world as the privileged class enjoying its privileges." But as pretty as it can be at Arena Stage, Philip Barry's classic comedy about class starts off uncomfortably stiff and stagy, and it is hard to reconcile some crucial casting choices, especially for those who remember the definitive performances of Katharine Hepburn and Cary Grant in George Cukor's 1940 movie version.

In a sunny sitting room, an uppercrusty Main Line family prepares for daughter Tracy Lord's marriage to stodgy nouveau riche George Kittridge. Tracy, a headstrong society golden girl who is kept on a pedestal by family and fiance, yearns for some liveliness and trouble -- which obligingly arrive in the persons of Tracy's raffish first husband, C.K. Dexter Haven, and a pair of reporters from a snoopy society rag, sniffing out a story on Tracy's philandering father.

Director Douglas C. Wager keeps Barry's bountiful laughs coming, and the 1939 play never feels dated. But Wager's efforts are hampered by casting flaws, which unfortunately begin with Tracy Lord, the fulcrum of the "Story." Statuesque Laila Robins certainly looks every inch the American aristocrat, but her Tracy is often sour and shrill, displaying little of the inner magnificence that makes her a magnet for men. John Leonard is too fey and flip as C.K. Dexter Haven, and there is no discernible emotional or intellectual heat or friction between him and Tracy.

Tom Hewitt is appropriately solid and stolid as Tracy's unimaginative husband-to-be. As reporter Mike Connor, Casey Biggs hits the right mark between gruff and goopy. With her bright, brittle and decidedly Hepburnish delivery, Cary Anne Spear, who plays photographer Liz Imbrie, might have made a good Tracy. Arena dependables Henry Strozier and Terrence Currier are most enjoyable as the incorrigible pinch-bottom Uncle Willie and errant patriarch Seth Lord.

The costumes by Ann Hould-Ward are a liability, in an array of dowdy shades and shapes that may have looked good on the sketch pad. The attractive, airy set, changing from a green-filled sitting room to a sculpture garden and back, was designed by Adrianne Lobel and sunnily lit by Allen Lee Hughes.

THE PHILADELPHIA STORY -- At Arena Stage through April 27.