For three days last fall, Chicagoans were stunned as a frantic car chase careened around city streets, with a policeman in a 1971 Chevy Malibu tailing a 1987 Oldsmobile Cutlass. The two cars screeched as they spiraled up the parking lot of the cylindrical Marina Towers. Then, as cameras rolled, the Cutlass vaulted off the 17th floor and plunged spectacularly into the river.

The filming wasn't for a glamorous action movie, but a commercial for Allstate Insurance, the "good hands" people who, along with their "good neighbor" counterpart State Farm, advertised for years with mild, homey messages promoting family and security. ( See the ad.)

Not anymore. Property and casualty insurance companies are engaged in a brutal marketing battle that has blown up those homespun images like a Hollywood stunt. Ad spending by the industry has grown more than 64% since 2000, to $2.89 billion, according to TNS Media Intelligence, and is growing faster than advertising for other competitive industries like wireless telecommunications, banks and prescription drugs.

The reason? Geico Corp., which has blanketed the nation's consciousness with an array of different campaigns, from pricey TV spots on NFL games to radio ads and billboards -- even banners flown by tiny prop planes. Its urbane gecko and indignant cavemen have won accolades and imitators and become cult figures. ("I just love those guys," Katie Couric said of the cavemen in a CBS Evening News segment last year.) More recent ads feature testimonials from real customers assisted by minor celebrities such as Little Richard and Verne Troyer (Mini-Me from the "Austin Powers" movies) who lauds Geico with an interpretive dance.

Geico's ubiquitous spokesreptile fronts an ad budget nearing a half-billion dollars. In response, St. Paul invented a menacing snowball (above) and Allstate sent a car plunging off a Chicago building (right.)

All told, Geico spent an estimated $403 million on advertising in 2005, and its ad budget rose another 20% in the first nine months of 2006, according to TNS. Coca-Cola Co, by contrast, spent $326.1 million on Coke advertising in 2005.

The once-staid unit of Berkshire Hathaway Inc. was pushing low-cost insurance and using the ad slogan: "15 minutes can save you 15 percent," as far back as the early 1990s, urging people to telephone for price quotes. The Internet made that model more efficient, with quick quotes online, helping establish insurance sold by price, not by agents, as a commodity. In such an environment, brand image is the key differentiator among rival companies, and advertising is paramount.

So Geico went into high gear. For years, it had relied on stodgy direct mail to woo customers. But the new tactics called for hitting television, radio and billboards, from all directions. Its ad spending soared about 40% in 2005, according to TNS.

Rival insurers were forced to pump up their advertising too, even though some say they offer personal attention and services, not just low prices. "In times of need or crisis the consumer needs someone beyond a talking animal," says Joe Tripodi, Allstate Corp.'s chief marketing officer. His reaction to the popular Geico lizard? "I'd like to squash it."

Geico still trailed Allstate, State Farm Mutual Automobile Co. and Progressive Corp. in private passenger auto insurance as of 2005, the last year for which figures are available. But its share of written auto premiums grew to 6.25% that year from 4.61% in 2001, according to insurance-rating company A.M. Best Co. Geico doesn't disclose detailed numbers, but analysts say it's profitable. "Not to mention that Warren Buffett continues to love them," says Donald Light, an analyst with Celent LLC.

"I love the advertising," confirms Berkshire Hathaway's chairman, who says he plans to boost Geico's ad spending by an additional 20% in 2007. Mr. Buffett also notes that without a sales force, Geico is dependent on ads to generate sales. The ad growth is "sustainable as long as I am willing to write the checks," he says, "And I love writing them."

The company's famous green gecko was partly the product of an accident. It enlisted the character in 1999 to help consumers remember the company's name, an acronym for Government Employees Insurance Co. The gecko was only supposed to be used for one ad. But an actors' strike forced Geico to keep using the reptile -- a fortuitous development since fans were beginning to email and call about him.

The small firm behind the ads, the Martin Agency, a unit of Interpublic Group of Cos., began adding other campaigns, including the popular cavemen in 2004. (In one recent spot, a caveman carrying a tennis racket in an airport spots a Geico billboard showing a caveman in a loin cloth with the tagline, "So easy a caveman can do it." He walks away, disgusted.)

Geico's prehistoric pitchman defends caveman contributions: 'Walking upright, discovering fire… sorry we couldn't get that to you sooner.'

The Geico campaign has vastly raised the Martin Agency's profile. The Richmond, Va., based firm has since landed other accounts such as Morgan Stanley 's Discover Card and Michelin SA's BF Goodrich.

Next up? Geico plans to blanket several sights in New York with ad messages, including toll plazas and the George Washington Bridge. Geico ads "need to be funny and need to get noticed," says Steve Bassett, creative director at the Martin Agency. "We try to use less Benny-Hill-type humor and rely more on David-Letterman type humor."

Allstate's humor is different. The new 60-second ad featuring the plunging car will debut during the Allstate Sugar Bowl tomorrow on Fox. As the Olds lurches off the building, pitchman Dennis Haysbert intones: "Now would be a good time to have Accident Forgiveness. Are you in Good Hands?"

To create the spot, which cost nearly $1 million, Publicis Groupe 's Leo Burnett hired director Phil Joanou (of the movie "U2 Rattle and Hum"). The three-day shoot required closing several busy Chicago streets, two stunt men and two cars taking the plunge into the cold waters.

Rival insurers are also employing pyrotechnics. The St. Paul Travelers Companies Inc. hired the special-effects company behind "The Lord of The Rings" movies to produce a spot dubbed "Snowball," in which a man tumbles down a steep street and picks up garbage cans, a car and other improbable items as he rolls. The massive ball explodes at the bottom of the hill, but everyone emerges unscathed and a voiceover chimes: "When you're in sync, you can roll with anything."