(FORTUNE Magazine) – Don't let the marching bands and busty, bathing-suited hood ornaments fool you: The legendary 24 Hours of Le Mans is not your average boys-and-their-toys auto race. It is serious--and potentially ruinous--business. Every June since 1923, some of the world's most powerful companies and most powerful men (along with some faltering companies and faltering men) have gathered in France's chateau-studded Loire Valley to vie for global automotive domination. For 24 long hours, the best drivers and competition versions of the most exotic sports cars strain to prove themselves in a marathon built of muscle, machinery, and money before 200,000 besotted fans. Why? Because winning Le Mans establishes engineering preeminence and carries huge bottom-line ramifications: When Mazda took first place in 1991--the first and only Japanese win--the company's sales jumped 30% the next year.

It's hard to grasp the idea that in the 24 hours it takes us to get from one Letterman broadcast to the next, a Ferrari prototype has screamed some 3,000 miles around Le Mans' 8.5-mile circuit at 9,500 rpms--stopping only to change drivers or the occasional set of tires. Forget the piddling two-hour screech fests of the Formula One and Nascar series: After 66 races (ten were missed in the event's 76-year history), Le Mans captures more spectators, driving talent, and dollars than any other motorsports event on the planet.

Maybe the draw is the range of automotive cheesecake on display here: big-ticket GT1s based on limited-production million-dollar-plus road-going sports cars; prototypes (purpose-built racing machines); and GT2s (modified "everyday drivers" like Porsche 911s and Dodge Vipers). Maybe it's the litany of racers who have tempted fate at Le Mans over the years--Juan-Manuel Fangio, Jacky Ickx, Bruce McLaren, Carol Shelby, Michael Schumacher. Or maybe it's the cachet that comes from winning the nearly unwinnable. In any case, drawn they are--some 28 teams, 48 cars, and 144 drivers.

Before the race, the start-finish line was clogged with a garish display of hyped drivers, rabid fans, and outlandish sheet metal. Near the front of the pack, Toyota's swooping carbon chassis looked more like a drunken brush stroke than a racecar. BMW's slab-sided open-top prototype showed no signs of lineage beyond its trademark kidney-shaped front grilles. Don Panoz's Panoz GTR, a hulking hawk-nosed batmobile, was a big hit with French fans (but then, the French like Jerry Lewis too). And dead last in the starting lineup sat a 911 GT2 painted with frolicking nudes and French-kissing lizards--quickly nicknamed the Porno Porsche.

At 2 P.M. sharp the green flag dropped, and the crowd--already ankle deep in a sea of beer cups--bellowed its approval as the cars thundered past. Then an eerie calm fell for nearly four minutes--the time it takes the drivers to lap the track, despite the fact that the fastest cars were hitting 240 miles per hour down the Mulsanne straight. The winning beast over the 24 hours, one of Porsche's factory GT1s, averaged 124 mph.

But the truly impressive numbers at Le Mans are financial. Manufacturers like Porsche, Mercedes-Benz, Toyota, and Nissan spend tens of millions to place their cars on the starting grid. Toyota, the near winner, spent an estimated $100 million (about $69,400 a race minute) to develop and run three German-built machines. And Nissan, despite financial woes at home, managed to drop more than $50 million on its four GT1 cars--and place third.

Even the smaller, independent teams put substantial cash into the race. This year's prototype-class winner, for instance, a Ferrari 333 SP, was funded by Doyle-Risi Racing, based in Houston. According to Wayne Taylor, a co-owner and the lead driver of Doyle-Risi, the team spent $600,000 on the Ferrari itself, another $400,000 on spare parts, and then roughly $550,000 on the Le Mans weekend. A transmission rebuild cost $25,000, fuel ran $6,000, brakes were $20,000, hospitality was another $24,000, entry fee $20,000. And so on. Dan Doyle, CEO of office equipment supplier Danka, ponied up much of that money on the theory that racing gives him an advertising reach no other medium can offer. "It brings us huge name recognition in Europe and Japan--our target," he says.

At midnight I wandered out to the first set of ess turns to watch the fireworks: Brake disks shone orange with heat, and downshifts shot long tongues of flame out of tailpipes. Despite the blackness, fatigue, and sporadic rain showers, each driver relentlessly held to a perfect line around the track.

With the kind of talent and silly money being poured into Le Mans, the potential for failure--and the pain of it--is huge. Toyota's car No. 29 led the race until a melted gearbox forced it to retire 90 minutes before the finish; mechanics in the Toyota pits wept. Mercedes-Benz and BMW each put two cars into the lineup this year, but within the first four hours all had fallen. Mercedes' sleek GT1s suffered from power-steering problems; BMW's two V-12 prototypes succumbed to wheel-bearing failure. Both German giants were horrified: Mercedes packed up every last three-pointed star, hospitality trailer, and jumpsuited technician and headed to Paris long before the end of the race--leaving many guests with no option but to find another party. BMW stuck around but shut its garage door to the outside world.

After the Champagne-soaked winners had endured a resounding "Deutschland-Lied" in honor of Porsche's one-two victory (its 16th Le Mans win--a record), I asked Doyle-Risi's Taylor what it felt like to drive through the night. "It can get pretty weird when you don't see any other cars for a long stretch," he replied. "You start to wonder whether you're out there all alone or not--some drivers can't take it." And what about driving so close to the edge for so long? "A lot of drivers get terribly motion sick. You're going so fast that it's almost inevitable." So much for the romance of speed.

I asked several teams what was next, and the response was universal: "Start preparing for next year." And, of course, "we really think we've got a shot."