A half-mile stretch of Eastern Avenue NE was transformed into a race track yesterday for this year's running of that annual spectacle, the Washington Soap Box Derby.

As the low-riding fiber glass and wooden cars rolled across the black-and-white finish line, spectators sought relief from the 95-degree heat under the shade of dogwood trees, sipping whatever could keep them cool.

Though the derby was started in 1934 to give youths a chance to learn about aerodynamics, sportsmanship and competition, it was the adults yesterday who seemed to be having the most fun.

"This event brings people from Maryland and D.C. together," said Al Simmons, an accountant who lives at 2906 Bunker Hill Rd. in Mount Rainer, just blocks from the derby site. "It's right here on the D.C. line. Neighbors meet each other here, and as a result, there's one less stranger in the world."

At least one of yesterday's 31 contestants disputed that notion. "What's important in a race is the car and the driver," 15-year-old Joseph "Stitch" Voegtli told a reporter moments before he was eliminated from the competition. "Each race is about half a minute. The slightest mistake could cost you. I'd like to win, but I just enjoy being here, too."

While yesterday's crowd of about 200 persons disappointed several members of the Downtown Jaycees, sponsors of the derby, for most observers the race retained the old thrills. "It's exciting and dangerous," said 11-year-old Marlin Wright, who came to the race with his father. "The photo finishes and stuff are real, ah, let me think of the word, um . . . it's exciting."

The official starter at yesterday's race, Kenneth Tomasello, 28, a chemical engineer and former derby racer from Arnold, Md., advised the drivers to "be careful of the bumps down the road, hold the steering wheel as straight as you can to the yellow line and make sure the brake is up."

"It's a game of inches," said Voetgli's father, William, who has had six of his nine children in the derby since 1976 and who yesterday pushed the button that automatically released the cars from the steel starting ramp at the top of the hill.

"A lot of work goes into these cars," he said. "They are built to wrap right around the driver," using minimum size, maximum weight and streamlining wherever possible. A senior-division car, with driver, weighs 250 pounds, he said.

"My kids have learned to be winners and losers by participating in the derby," said the elder Voegtli. "That's just like life. Most of the time you lose but, when you win it's great."

Much about yesterday's race retained the old traditions. Gravity was the only horsepower for the cars, which reached 35 miles an hour as they sped down the steep hill that peaks at Kaywood Place and flattens out at Varnum Street NE, near the red-brick Northeastern Presbyterian Church.

There was a new twist for the 26 boys and five girls who raced in yesterday's derby: Both top winners were female.

Martha McGowan of Rockville won first place in the senior division, and Christine Tivel of McLean took the junior-division championship trophy. They will go to the National Soap Box Derby in Akron, Ohio, later this year.