(FORTUNE Small Business) – It's 6 A.M., and an older man is running through the aisles of the Brimfield Antique Show, 90 minutes southwest of Boston. "Any poker chips?" he pleads at each booth he passes. "Anything gambling-related?" A dealer in Civil War artifacts eyes him warily and says no. The man dashes off, the echo of "Poker chips? Poker chips?" trailing faintly behind. Another man follows, asking, "Any political or sports memorabilia?" The second man has been up since 3:30 A.M. to be first through the gates. Caravans of cars and trucks are still rumbling into massive parking lots nearby; by 8:30 A.M. traffic into town will be backed up for three miles. This may seem like extreme shopping, but it's actually pretty typical at Brimfield, the largest outdoor antique show in the U.S.

As a child, you probably collected coins or stamps or knew someone who did. Today collecting is big business--and it's not just for kids. Thirteen million viewers watch Antiques Roadshow each week, making it the highest-rated prime-time show on PBS and inspiring spinoffs on HGTV and A&E, among others; eBay is even planning to launch a syndicated show, starting next year. Online, eBay has 46 million registered users (double the number two years ago), who spent $11 billion on auction items in 2001. But although you can now buy and sell antiques from your living room, there's something especially satisfying about an outdoor fair, where you still get to handle the goods, ask questions, and take in a combination of fresh air and fried dough.

The first Brimfield show was held in 1959 when auctioneer Gordon Reid brought 67 dealers to the 40-acre lot behind his home in this sleepy rural town. Today Reid's daughters invite 800 dealers to that same lot three times a year--May, July, and September--and other landowners along Route 20 have joined in, drawing a total of 4,000 dealers and as many as 100,000 shoppers to the mile-long strip. (This month's show is Sept. 10-15; www.brimfield.com.) Admission to most fields at Brimfield is free, though some charge a few dollars on opening day. You can find other antique shows at this time of year, but as Priscilla Levy, who flies in from Thousand Oaks, Calif., specifically to shop, puts it, "If you haven't done Brimfield, you haven't lived!"

It's nearly impossible to count--or even identify--the variety of collectibles for sale. Next to a punched-tin folk-art cabinet ($3,400), you might find a pair of polished-brass stirrups from old-time shoeshine booths ($150), or a brass-and-iron cigar cutter in the shape of a parrot ($495), or a woven purse made entirely of Pall Mall cigarette packs ($175). Not everything is one of a kind--there are plenty of CorningWare mixing bowls and 1980s school globes showing the Union of Soviet Socialist Republics. Nor is everything expensive. Pouty 1947 pinup girls from Esquire magazine go for just $5 each.

Because the show is so big, and because the booths aren't organized by subject, some families opt to split up, keeping in touch by walkie-talkie. Others try to speed up the search process by wearing their collections on their sleeve--literally. T-shirts read I BUY HARMONICAS and BUY/SELL WEDGEWOOD. One man wears multiple signs reading MEDICAL ANTIQUES, DENTAL ANTIQUES, EYEGLASSES. Do the signs work? "Of course they work!" he scoffs. "I've been wearing them for 40 years!"

Dealers also do what they can to stand out. David Young, 46, a dealer from Orange, Mass., parks his blue 1951 General Motors tour bus in his booth, using it as a showroom for his guitar-shaped Elvis clock, Pete Seeger records, and other 1960s and 1970s kitsch. Outside the bus, the rest of Young's wares fall into a much broader category, one very popular at Brimfield--"anything that will sell." On this day Young has an electric fan, a wooden school desk, various hood ornaments, and a seven-foot fiberglass tiki head ($225 and ideal if you're looking to stage South Pacific). Young knows the tiki is a long shot to find a buyer. "Someone might want it," he says, shrugging. "Check back later."

It's tough to turn a profit in the antique business, and the dealers who try often describe themselves as hopeless addicts. Frank and Jean Consentino spend four months of the year driving their Winnebago from New Hampshire to San Diego and back in the tireless quest for elegant Depression glass. "It's different from regular Depression glass in that it's blown, not pressed," Frank will tell you, along with as much glass history and minutiae as you can handle. (Inquire about etching techniques at your own risk.) He has more than 2,000 pieces in his personal collection, and as a dealer, he's been selling goblets, pitchers, and punch bowls for 25 years. "Customers come back each year," says Jean. "We remember customers who came to Brimfield as kids and now bring their kids. They become our friends."

Friends, that is, who like to haggle. Everyone wants the thrill of a bargain, and price tags are only a starting point for negotiation. Most $18 items will go for $12, most $12 items for $10 or $8. Get in the spirit, and you'll find yourself wheedling a $3 pair of enameled Santa earrings down to $2. Shop a little longer, and you may begin to see a $200 chamber pot from the 19th century as a must-have, along with the Rod Stewart eight-track tapes, a steal at $3 apiece, even if you don't own an eight-track player. That sort of thinking is your cue to go home. A last stop back at the bus brings sad, if not unexpected, news: David Young's tiki did not sell. Amid the late-day shoppers, he relaxes in his plastic Herman Miller chairs ($35 each). A woman approaches, asking about a well-water hand pump lying on the ground in two rust-covered pieces. Young hesitates before pricing it at $40. Why would she want it? "I don't ask," he says after the woman passes. "I don't even ask myself. There's no accounting for taste."