NEW YORK -- About 20 minutes into "Steel Magnolias," a rollicking and altogether endearing first play by Robert Harling, there is a sudden shifting of gears that signals the presence of a gifted playwright and indicates that he is very likely to make good on the evening's abundant promise.

Up to that point, the play, which is shaping up as a considerable off-Broadway hit at the Lucille Lortel Theatre, has been robustly funny. Harling is obviously an observant writer with a sharp eye for the idiosyncrasies of southern womanhood. "Steel Magnolias" begins by chronicling a particularly busy April day in a small-town Louisiana beauty shop -- a transformed carport, actually, dedicated to the proposition that "there is no such thing as natural beauty."

Truvy, the good-hearted proprietor, has just hired an assistant, who in her goggle-eyed nervousness tends to produce hairdos that are overly "pouffy" even by southern standards. The customers will soon be coming in to get teased and fluffed, and the morning promises to be chaotic.

It is, you see, the wedding day of the town beauty, a certain Shelby, and excitement is running high. The bride-to-be insists on a bouffant, sown with baby's breath -- just like Princess Grace in the photo she's brought with her. Shelby's mother, M'Lynn, is understandably edgy and frets that the all-pink wedding motif "makes the sanctuary look like it was hosed down with Pepto-Bismol." Clairee, the aged widow of the town mayor, can barely hold her curiosity in check and is succumbing to a teen-ager's sense of mischief.

As the women trade gossip, good-natured jibes and reflections about men, marriage and the latest styles in "Southern Hair," "Steel Magnolias" is off to a hilarious start. Then Shelby abruptly turns ashen and slumps over in her chair. She's having a diabetic insulin reaction.

She has them often, so none of the characters is unduly alarmed by her spasms. They pat her hand, hold her head, try to get her to sip some orange juice and wait for her to come out of it. In short time, she does and the merriment and ribaldry resume. But in that momentary surcease of high spirits, Harling has deftly served notice to his audience: His play is not to be just another caricatured romp through a redneck backwater.

Comedies about the South -- of which there seem to be a plethora these days -- tend to paint it as the land of rampant eccentricity, not to say heat-induced retardation. There are usually dead animals on the road and pistol-packing loonies in the garden. The food is as sweet and syrupy as the accents. Indeed, to Shelby's dismay, the groom is providing a cake in the form of an armadillo -- red on the inside, gray frosting on the outside -- and she worries that when it's cut, people will think it's bleeding.

Harling has more on his mind than mockery, however. Without ever abandoning its sense of the ridiculous, "Steel Magnolias" proceeds to display a heart as big as a watermelon. In four scenes that cover nearly four years, the characters are revealed as courageous, supportive sisters under the scented skin. Issues of life and death will intrude on the rituals of this beauty shop and catch the banterers off-guard. But they are never long without a response, a gesture or a quip that will ease life's hurt, if not mend it.

"Steel Magnolias" is one of the most persuasive plays I have seen about the way women minister to one another, the intimacy they enjoy among themselves and the intuitive understanding that binds them in moments of joy and pain.

"Time marches on," observes Truvy with resignation, before adding, "and eventually you realize it's marchin' across your face." That kind of fillip is characteristic of the play, which could be accused of courting a maudlin sentimentality, if it weren't so adroit in its mixture of laughter and tears. "Laughter through tears is my favorite emotion," confesses Truvy, after the play's turbulence has given way to healing humor. I suspect that is also the playwright talking.

He is masterfully served by a first-rate cast, headed by longtime soap star Rosemary Prinz, as Shelby's mother. At first, Prinz projects a deceptively ladylike authority -- firm and slightly acidulous with the wryness of one who knows what's best for her daughter, even if her daughter doesn't. Then, she slowly peels back the fac ade and shows us the depths of her love and gallantry. It is a noble, self-sacrificing performance by an actress who does everything not to appear noble.

As Shelby, Betsy Aidem has a sunny optimism that refuses to acknowledge the realities of her health or the toll that childbirth will take on her. "On cloudy days, I feel God isn't tryin' very hard, so I don't have to either," she observes, gaily. But she doesn't really believe her quip and treats clouds as impertinent intrusions on the landscape. If she is headstrong, she has put her obstinacy in the service of life and there will be no more talk about it.

Lovely, that. And lovely, too, the pixieish delight that dances in the eyes of Kate Wilkinson, the town's former first lady, who isn't going to let a little dignity get in the way of having a good time. In that respect, she would appear to be the antithesis of Ouiser, the local grouse who announces peremptorily upon entering the shop, "Don't try to get on my good side, because I don't have one."

As played by Mary Fogarty, Ouiser is a rare curmudgeon, her patience as short as the thatch on her head. When someone remarks that things can't get much worse, she's quick to snap, "Of course, they can." Fogarty's accomplishment is to suggest the simmering warmth under the crust. She may be a hard old nut, but deep down she isn't fooling anyone. This nut can be cracked and she knows it.

Attending to their beauty, anticipating their needs and keeping up the running jokes, Margo Martindale gives Truvy the sassiness of Madge the Manicurist, the wisdom of Montaigne and the solicitude of a mother hen. Even Constance Shulman, as her gawky assistant, transcends caricature. A cartoon on the loose, you're apt to think -- all sharp elbows, bony knees and distracted wits. But you think wrong. There's a person here, too, who'll flower once her jitters abate.

Distinct as they all are, they form a society far greater than its individual parts -- a dramatic amplification for which director Pamela Berlin is clearly responsible. Berlin appreciates what makes these women unique. But she also celebrates their shared humanity and the emotional sustenance they provide one another.

In the course of the evening, a lot of hair is washed and rinsed, tinted and set. But that's the least of it. Truvy's is a port in the storm. Here, spirits get bucked up, the broken heart is mended, and the flagging will to carry on is recharged.

Women, I suspect, will instinctively acknowledge the truth of Harling's play. Men can see what they've been missing. We have the barber shop, I suppose, but after watching "Steel Magnolias," I was obliged to admit the barber shop is just a hollow, blustery place for a shave and a trim. And you're back out on the street again. Steel Magnolias, by Robert Harling. Directed by Pamela Berlin. Sets, Edward T. Gianfrancesco; lighting, Craig Evans; costumes, Don Newcomb. With Betsy Aidem, Mary Fogarty, Margo Martindale, Rosemary Prinz, Constance Shulman, Kate Wilkinson. In New York at the Lucille Lortel Theatre.