Pity the poor upper-class folk. It's so hard to fall in love, what with Andy failing to waltz with Melissa at the dinner dance she had invited him to and spending all that time rowing and all. It takes these two 50 years to get it on, as it were, but they stay in contact (if not in touch) all that time, a testament to the complications and joys of human contact.

"Love Letters," which opened last night at the National, is not just a moving and funny chronicle of love among the WASPs, which it is, but it reaches out to touch the Yalie in all of us. Playwright A.R. Gurney, the bard of the plaid pants and martinis set, pokes fun affectionately and pointedly, and in the end we unexpectedly find ourselves dabbing (discreetly) at tears, sorrowing at the loss of love and friendship.

It should be said that "Love Letters," which I saw Sunday in Wilmington, is not really a play. It is two actors -- in this case E.G. Marshall and Colleen Dewhurst -- sitting side by side at a table, reading from letters sent between the fictional Andrew Makepeace Ladd III (the kind of guy who might have been called Trey or Andy 3) and Melissa Gardner, who met in second grade in 1937.

The piece has proved to be a durable two-hander since its debut at the New York Public Library in 1988, and here marks the return of former Kennedy Center chairman Roger L. Stevens as an independent producer at the National Theatre. It is a natural for touring, as it has practically no set, needs little rehearsal (the actors read from scripts), is less than two hours long and provides two lovely parts for actors of all ages. Indeed, more than 100 name actors, and untold numbers of less famous ones, have performed it in the last two years, from such unlikely choices as Patrick Cassidy and Valerie Bertinelli to the likes of Julie Harris, Charlton Heston, Kitty Carlisle Hart and Christopher Reeve, to name but a few.

It's hard to imagine any of them being better than Marshall and Dewhurst. Dewhurst's husky, I've-done-a-lot-of-things-I-shouldn't voice is perfect for the wayward Melissa, the rebellious daughter of a family endowed with wealth but little affection. She grows with Melissa through her mischievous grammar school days, the "crappy" boarding school from which she is bounced for "nipping gin in the woods with Bubbles Harriman," her short career at Briarcliff and early flowering as an artist. Melissa marries a suitable Wall Streeter, sets up house in New Canaan, has two children and becomes an alcoholic. The years do not treat her kindly.

Marshall is equally in tune with stuffy, righteous Andy, the soul of rectitude, who does the right thing whenever he can. Summa at Yale (and Scroll and Key, one of those archaic secret societies for seniors), then the Navy, Harvard Law -- where he makes Law Review of course -- then clerking for a Supreme Court justice, marriage to a proper girl, partnership in a prestigious Manhattan firm and a seat in the U.S. Senate. Only twice does he stray from the predicted path. He has a serious affair with a Japanese woman while he is in the Navy -- but leaves her in the face of his parents' objections. And, well into middle age, he and Melissa finally requite their love, an autumnal blaze of passion that delights them until Sen. Andy calls a halt for fear of voter disapproval.

It is Andy who starts the correspondence and (with occasional pauses) keeps it going. His father told him letter writing is "a dying art." But there is more to it than that -- his letters express his secret soul, the emotion and directness he cannot muster in person. Melissa resists at first; she hates writing letters. At different points in their friendship she urges him to call long distance instead and blames "all these goddamn letters" for an unconsummated weekend at Yale. But she comes to need their correspondence -- and the reliable friendship it represents -- as much as he does.

"Love Letters" is not about the letter as a "dying art" but rather about a relationship as revealed by the scraps and scribbles that were left behind. It is about history as well, about knowing someone almost your entire life, through periods of intimacy and anger and times when the desire for closeness is not equal.

Gurney is particularly brilliant at capturing the great range of missives we send each other, from the awkwardness of a second-grader's thank-you note to the phonily intimate mass Christmas letter. (She writes back threatening to "stand up on my chair and moon" his entire proper family if he sends her one again.) There are wedding invitations and properly worded regrets to same, announcements of appointments and art shows, and long boarding-school plaints filled with adolescent slang and self-conscious vulgarities. There are also silences, letters sent but not answered. For a while.

They freely criticize one another. When Melissa sends him a card from summer camp that reads, "You made me promise to send you a postcard. This is it," Andy writes back with a list of things she could have written about, such as "Are your parents really getting divorced?" and "Is there anyone there my age?" (She writes back a terse list of answers: "Yes. No.")

She writes that her mother gets drunk all the time; he tells her about "stroking the fourth crew" and then maybe being "number four on the fifth" and on and on. She replies that "your last letter was too much about rowing." He writes that his grandfather told him not to be first in his class, because "only the Jews are first," although, he notes, there are no Jews in his prep school. There are some Catholics, but "Catholics are not too smart."

A few of the darker notes are left hanging; he, the lawyer, won't help her get back custody of her children, for example, and yet that doesn't seem to affect their relationship. She never seems to find herself, bouncing from relationships to dry-out tanks to failed artistic attempts with a desperation that is never resolved.

But in the end -- and there is an end -- we are happy to have known these two old preps. They would be 60 now, and touched by a world larger than the hidebound, privileged one they grew up in. The best love letters are not sent by lovers, but by friends, and they are more likely to last too.

Love Letters, by A.R. Gurney. Produced by Roger L. Stevens, Thomas Viertel, Steven Baruch and Richard Frankel, directed by John Tillinger, lighting by Dennis Parichy. With E.G. Marshall and Colleen Dewhurst. At the National Theatre through Nov. 11.