Not every time you shop for an evening gown does the magic happen. Maybe only once or twice in a lifetime do you try on a dress you know is perfect.

For that party, or prom, or for the high school reunion - you know this is the dress. For that dinner. For that dance.You desire it. You bend your budget to get it. You want it for the way it makes you feel: exotic or thin, bold, elegant or graceful. Mysterious, perhaps. Or just plain gorgeous.

The one dress.

New York designer Christian Francis Roth says The One Dress should be bright, like the Amish country quilts that inspire his fall collection. Like a quilt, his evening dresses are meant to be treasured, to be worn and passed down to daughter or granddaughter.

Randolph Duke believes if you are going to spend money on evening wear, you should invest in something wild. He pairs a short plaid organza or chiffon skirt with a shiny silver jacket for a Catholic-schoolgirl-joins-a-motorcycle-gang look.

The fabric is most important to Oscar de la Renta. For fall 1991, he likes the rustle of taffeta, the shine of sequins, theflow of chiffon. His designs are classic. They, too, if well-cared for, could become heirlooms.

Sophistication is what evening wear is all about for Jennifer George and Donna Karan. George shows gray flannel with gold sequins. Karan likes slinky black knits wrapped with gold metal belts.

Quite a few designers equate "evening" with "lingerie." Slip dresses, worn over lace or fishnet stockings, abound. Yeoleng Teng shows slip dresses with empire waistline. Others show a simple chemise.

Geoffrey Beene likes satin pajamas for evening. Bill Blass includes a "dressing gown," a short, tailored dress of rust panne velvet. (The fabric recalls a couch, circa 1960.) In keeping with the lingerie look, Calvin Klein shows gold and silver lace, molded to the model. Marsia Trinder and Nuala Boylan (the Trinder & Boylan label) like wool plaid jackets over short, full, black lace skirts.

And as popular as the slip is the coat dress. Michael Kors shows a perky black-and-white-striped satin version.

Jewel tones sparkle best at night, according to Adrienne Vittadini. She tops sequined sheaths with coats of turquoise, green or purple.

Bob Mackie likes bright red for evening, in everything from a Lycra jumpsuit to a huge tulle creation that looks like a wedding dress.

Laura Ashley likes black velvet. Charlotte Neuville likes bright pink satin. Or shiny black satin, covered with a white quilted coat.

But what about us? What do Utah women like to wear for evening? When asked, several said, yes, they do have a very wonderful dress, right now, hanging in their closets.

Colleen Bangerter treasures the dress she wore to the Governor's Ball as our new First Lady. She also wore it to the White House once, for dinner.

"It's a tea-length pink chiffon," she says. "It fits well. Makes me feel good. Feminine."

For gymnast Missy Marlowe the best dress is the one her grandmother bought her. "It's kind of a bright-colored flowered print with a white background, off the shoulder, scalloped design. I love the neckline," she says. When she gets older, she says, she's planning on wearing something a little more slinky. Perhaps something with clear rhinestones. "Nothing gaudy."

Lynne Zimmerman, press secretary to Salt Lake Mayor Palmer DePaulis, says her favorite evening gown is one she wears often. It's black, with silver threads outlining a geometrical design. "I love to wear black at night," she says.

Her husband, Michael, smiles, thinking of another dress. "I always remember the one you wore when we were going out," he says. "It was white, no back, with crisscross straps. Remember? You wore it to the Governor's Ball, back when they held it at the Terrace Ballroom."

Over a decade, the memory lingers. "You were swimming a lot then," he says, smiling again.

Ellie Muth, district merchandising publicist for J.C. Penny, remembers her high school graduation dress. "It was blue, shiny cotton, with little spaghetti straps." She bought it in 1954. She and her mother drove from their home in Modesto to San Francisco to make the purchase. "I picked grapes all summer to pay for that dress."

"And you know," she adds, her voice growing warm with excitement, "it had a lace panel in the front with little blue bows going all the way down.

"I still have that dress. It was so expensive, I could never bring myself to pass it on. I've moved all over - and I've always hauled that dress."

That one dress.