With the number of charity balls on the rise -- there will be more than 100 fund-raising events in Palm Beach, Fla., alone this winter-spring season -- retailers and designers are creating complex new customer-tracking systems to avoid an age-old problem: a party-goer showing up for a gala in the same high-end gown as another guest.

Sami Alpark, owner of the Alpark boutique in Palm Beach, sold a client a $5,200 dress by Eavis and Brown of London for a local society event. Yet in doing his due diligence by talking with the event's organizers and other retailers, Mr. Alpark learned that a woman from England planned to wear a dress by the same designer. Mr. Alpark camped out in front of the British woman's hotel and offered her another gown, gratis, for her to wear instead. She accepted.

"I could never let my client suffer that embarrassment of being seen in the same gown or even the same designer as someone else," he says. "It's a matter of principle."

The growth in charity balls has exacerbated the problem. While no one tabulates the number of fund-raising events nationwide, charity experts say they have been on the rise along with the growth in giving. (Americans gave $260.3 billion to charity in 2005, up 6 percent from 2004, according to Giving USA.)

What's more, today's top designers such as Oscar de la Renta and Badgley Mischka are cranking out ever larger quantities of their most popular gowns, making it more likely that fashionable socialites will see their double on the big night.

"The problem has certainly grown," says Terri Eisenfeld, a partner in the Zola Keller boutique in Bonita Springs, Fla. Ms. Eisenfeld says she got a call from an angry customer who had purchased an $800 Giovanni dress from the store only to see another woman in the same dress at the same event. "The other woman bought the dress somewhere else, so we didn't know about it," she says. "But our customer was still very upset."

Even the First Lady has fallen prey. During a White House gala last month, Laura Bush wore an $8,500 red Oscar de la Renta gown -- as did three other women at the event. Mrs. Bush dashed upstairs for a quick costume change, but not before camera crews captured the fashion foul-up for the evening news.

In Palm Beach, where the black-tie ball season is in full swing, stores are scrambling to prevent similar gown wrecks. At Luca Luca, store managers write down every customer's name and note for which events they are buying a dress. The boutique carries only one gown of each design, and coordinates with its other stores to make sure none of its customers buy the same costume for the same event.

The Carolina Herrera boutique in New York similarly asks each customer to which events they plan to wear their dresses so it can be recorded in a log. Yet the store admits it can't keep track of the same Herrera dresses sold at nearby Bergdorf Goodman.

Alpark in Palm Beach keeps an Excel spreadsheet listing its clients and the dresses they bought. The spreadsheet is then cross-referenced with the Palm Beach social calendar to avoid customer clashes. The store also employs a full-time client-services manager who, among other things, cross-checks all the client gown plans.

Yet though the stepped-up tracking systems can prevent dress disasters, they also can create other anxieties. "The hard thing is when a customer comes in and wants the dress for a certain occasion and you tell them someone else already bought it for the same event," says Bea Reid, manager of the Luca Luca boutique in Palm Beach. "In that case, it's whoever bought first."

And woe to the ball-goer who patronizes a store that doesn't cross-reference its customers. Last year, Palm Beach socialite Lori Stoll attended a charity event at Donald Trump's Mar-A-Lago Club and during cocktails noticed another woman wearing the same black-satin two-piece outfit. Ms. Stoll had bought the dress for the relatively low price of about $500 at a mall-based store.

"My heart dropped for a second," says Ms. Stoll, a tanned brunette whose husband is a concert promoter. "It made me think of those celebrity magazines where they have two stars wearing the same things and they ask, 'Who wore it best?' It was potentially embarrassing."

Ms. Stoll took the faux pas in stride and greeted her fashion twin with a smile. "I said, 'Well, we both have good taste!" And she learned her lesson about buying lower-priced gowns: "Now I just stick to high-end couture."

Some women are venturing to fashion capitals such as Milan and Paris to buy unique, haute couture dresses they know aren't likely to show up in their hometowns. Annie Falk, who frequents charity events in New York, the Hamptons and Palm Beach, sticks to sample sales offering one-of-a-kind dresses and trunk shows, or visits vintage-clothing shops. "When women go out and try to find the hottest item of the season, that's when you run into trouble," she says.

Just as humiliating as the gown wreck, however, is being photographed in the same outfit at two different events. Tiffany Spadafora, whose photographs are a staple of Palm Beach's society publications, wore a black-and-white Oscar de la Renta number -- one of about 50 high-end gowns the young socialite owns -- to a firemen's benefit ball last year. When her photo didn't appear in the next day's papers, she thought it was safe to wear the same dress to a ball photo-shoot for a local society magazine. But Town & Country magazine picked up the firemen's ball photographs, and she suddenly found herself on the local magazine stands wearing the same dress to two events.

"I have to retire that dress for a while," she says of the $5,000 gown. "It's sad, because I really liked it."