Several hours before Jim Stirling's Chrysler station wagon was reduced to a smoking carcass of twisted steel, the whole family gathered in his driveway to lavish it with love.

It had taken several late nights under the hood, but Stirling now had the engine purring. The wagon's new coat of black paint glistened in the morning sun. Stirling's wife, Angie, held their 2-year-old daughter, Brooke, on her hip to help apply a finishing touch.

"I love Daddy," Brooke wrote -- with her mother's help -- in crooked gold letters on the wagon's rear panel. She switched to red marker and drew a heart over the gas cap.

There was only one thing left to do to the car: destroy it.

"It's a family thing," Angie Stirling said.

Some families take their station wagons on leisurely weekend road trips. But on four Saturdays every year, the Stirlings, who live in the rural Southern Maryland outpost of Mechanicsville, take their cars to the demolition derby.

It's a tradition that started with Drew Stirling, 51, the stout patriarch and plumber who has been crashing cars for more than 25 years. For two years in the late 1990s, he stopped driving and worked as a track official overseeing the derby. But the itch to compete was too strong.

"It's all about the adrenaline," he said. "I realized I'm not going to give up the derby. Well, when I'm in a wheelchair, maybe."

His sons, Jim, 31, also a plumber, and Robert, 26, a former Marine who works at an industrial supply shop, grew up with a detailed knowledge of motors and a passion for collisions. Both competed in their first derbies as teenagers, before they could drive legally. It is a family of buzz cuts and mustaches, blue jeans and dirty hands. To strangers, the Stirling men can be stoic and taciturn, but among friends and on the topic of cars, the words spill freely.

"When they're not working on their cars, they're talking about their cars," said Angie Stirling, who runs a day-care center at her home. "They love it, the kids love it."

Saturday's demolition derby was held at Potomac Speedway in Budds Creek. It was put on by the Silver Hill Lions Club. After 32 years at several different venues, it has grown into the largest derby in the state, organizers say, attracting capacity crowds of more than 2,000 people to the muddy track in Charles County. The winner takes home $1,000, a trophy and a black champion's jacket.

The actual competition involves about 20 cars gathered in a 60-by-120-foot enclosure. They line up on two sides with the rear ends of the cars facing each other. The crowd chants along with the announcer, who counts down, "10 . . . 9 . . . 8 . . ." On the signal, the drivers step on the gas and ram into each other in reverse. The unmuffled cars roar like monster trucks, and the spinning tires shoot mud into the cheering crowd.

The bodies of the cars, which have been stripped of all glass, chrome and any extraneous fiberglass or plastic that could become a projectile, careen around the track and smash like beer cans. Pintos are prohibited.

A firetruck waits to put out any flames. The five cars that survive each heat move on to the finals, and the last driver still hitting is the champion.

It can be a painful pastime, although participants tend to play down the risk. Theda Smith, 42, of Manassas said she once smashed her face on the steering wheel after a violent collision, got knocked out and had blood streaming down her chin. Her husband, Stanley Smith, 45, had three teeth knocked out during one competition. Both were wearing helmets.

On Saturday, Stanley Smith, an electrician, was wearing a knee brace and taking blood thinners for a clot in his leg. His doctor told him not to shave with a razor in case he got nicked, but he wouldn't be kept out of the derby. "I'm not going to stop doing what I want to do," he said. "I just want to hit something."

The real trick, the drivers say, is to find the right car, and that can be a year-round pursuit. The Stirlings are always on the lookout for derby cars, preferably sturdy eight-cylinder Fords or Chevrolet wagons from the 1960s or early 1970s.

Drew Stirling found the 1972 Oldsmobile he drove in a recent derby while on a plumbing job. He slipped his business card on the windshield, got a call two hours later from the owner and for $175, it was his.

Once drivers find the proper junker, it is a matter of stripping it down -- removing the windshield, dashboard, back seats, upholstery, antifreeze and Freon. Some put padding in the driver's-side door to cushion the blow, but not the Stirlings. They all pitch in to tweak each other's cars, securing the battery, welding the doors shut or sawing off the exhaust pipe. Angie Stirling makes the derby T-shirts and sometimes paints decorations on the cars' hoods.

Winning is not everything, the Stirlings say, but the family has had some success. In September, Jim Stirling won the Charles County derby. On June 5, he also won the Outlaw Derby, a competition for modified cars that paid out $3,000. If they are ever in the same heat, the Stirlings will work together to smash other cars and protect each other. But if it comes down to just family, such niceties are abandoned.

"I'm going to hit them, and they'd hit me," Drew Stirling said. "I don't come down to the derby to shut it off. I come down to hit somebody."

This weekend, it didn't get to that point. Robert Stirling's 1976 Ford Thunderbird, "The Punisher," had its battery busted and went out in the first heat. His brother and father both advanced to the finals, but their cars died while the "Derby Dogs" from Virginia were still pounding.

Drew Stirling's Ford wagon took the most vicious beating. By the end of the competition, his rear bumper was gone, he had two flat tires, the front seats were broken and every panel was hideously smashed. The crowd especially appreciated when his engine caught fire and smoke billowed around his head.

When he finally crawled out of a window and hopped down into the mud, his round face was red and sweaty, his smile from ear to ear.

Drew Stirling, in car at top, and sons Jim and Robert mix it up during the demolition derby at Potomac Speedway in Budds Creek. Robert Stirling, a former Marine who works at an industrial supply shop, fastens his helmet before the start of Saturday's first heat.Jim Stirling carries his trophy from the previous week's Outlaw Derby past crowd members Saturday. The Outlaw Derby, for modified cars, paid out $3,000.