Pre-worn children's clothes have gone the route of pre-washed denim: They're hot.

No longer do mothers park around the block and sneak into -- wearing hats pulled down over their faces -- used-clothing shops. They pull right up to the door in their Mercedes, plunk down Gucci tote bags crammed full of their children's outgrown clothing (for consignment), and browse boldly through the racks looking for outcast Florence Eisemans, Pierre Cardins and Billy the Kids.

In our new cost-conscious economy, buying used children's clothing is not only practical, it's chic.

"We have diplomats, embassy women of all nationalities and even Cabinet wives," says Betty Belfiore, owner of Kids' Stuff, an Upper Northwest consignment shop that sells only children's clothing. "We cater to middle class and upper middle class -- it's not a thrift store for the needy. Customers are conscious of styles and prices and want a bargain at that."

Most used clothing stores claim they save you between 25 and 75 percent off retail costs, but there are tales of even greater bargain finds.

Falls Church mother Wendy Ernst says that 90 percent of the clothes worn by her two small children are pre-worn. "Kid's don't wear clothes long enough to invest in them," she says, "but now it's more popular and you have to look harder. People never used to talk about it, but I would say that nearly every mother I know talks about going to rummage or thrift sales now for kids' clothes."

Some examples of items recently on the racks at Kids' Stuff: a Sylvia Whyte cotton dress which retails for $42, at $26; a boys terrycloth Pierre Cardin baby set for $5, and ballet slippers, $4.50.The average price in the store, however, is about $3.50.

Belfiore opened her store five years ago after polling friends about what they thought about shopping for their children in used clothing stores. "Most found consignment shops stuffy, unorganized and not particularly fond of children accompanying mothers on shopping trips."

Kids' Stuff has two brightly decorated rooms, well marked and organized racks by size, and kids are welcome. There's a special play area and even a special kid's bathroom. ("The minute you take a kid someplace," says Belfiore, "he tells you he has to go.")

The Kids' Stuff accepts consignments Tuesday and Thursday. "There is no rule of thumb on pricing," says Belfiore. "We take into consideration the condition of the item, the brand, of course, and the style." The consigner and the store get a 50-50 split.

Kids' Stuff is one of the few consignment shops stocking only children's clothes. Most carry men's, women's and children's under the same roof.

"We've seen a tremendous increase inour children's business since we've one through the tight money situation -- double-digit inflation has done wonders for our business," says Betty Lorino, assistant manager of the Junior League Shop in Georgetown, which has a special section for qualtity children's clothing. "Some people have said that this store has dressed their families as they've grown up."

The Junior League accepts consignments daily, but only by appointment, and sometimes the waiting list is long. The customer gets 60 percent and the rest goes into the community trust fund for League projects.

At Reprise in Bethesda, run by the Jewish Social Service Agency, income tax time and warm weather have brought a flood of customers.

"We were lucky to have gotten the goods of two stores of children's clothes that went out of business," says manager Betty Frank. The store is selling Levis boys pants for $6 ($12 normally) and infant dresses for $7 that sold for $34.

If you're interested in selling outgrown children's items by consignment, check selling arrangements in advance. Most stores will keep clothing on the racks only for a certain amount of time, after which you must pick up your unsold items, or they are donated to charity. Your percentage of the selling price also varies from place to place. (It is usually 50-50, 60-40, or 40-60.)

Stores like things that are current: Playclothes don't change styles much, but dresses and jackets should not be over three years old.Items sell if they look fresh, with no stains or tears, are laundered, pressed and starched.

If you're shopping for kids in consignment or thrift stores, shop early in the season for the best selection. Look for brand names; they last longer. There's one Florence Eiseman dress that keeps reappearing every few years in the Junior League Shop. It just won't wear out.

Also look for merchandise with original price or store tags. Consignment or thrift stores often get goods from stores that go out of business. They also may get the overflow from children so innundated with expensive clothing that they just don't have time to wear it all.

Another suggestion offered by inveterate shoppers: Read the weekend want-ads advertising garage sales. If children's clothes are listed, call to find out sizes. And then go early.

And where will you find the best buys? In neighborhoods better than your own.