Dean Matthews, a world-class runner in a people's race, took the lead just past the one-mile marker and, with a regularity that almost bordered on monotony, extended it to more than 1 1/3 minutes in winning the sixth annual Marine Corps Marathon in a record 2 hours 16 minutes 30 seconds yesterday.

Matthews, 26, a salesman from Atlanta running his first marathon in almost two years after suffering a back injury, broke the 3-year-old course record of 2:18.08 set by Scott Eden of Richmond.

Cynthia Lorenzoni, 23, of Charlottesville, running her first marathon race, finished first among the women in 2:50.22, good for 343rd overall. Lorenzoni, who works part time in a sporting goods store, passed Beth Dillinger of Blacksburg, Va., at the 12-mile marker on the Mall near the reflecting pool at the foot of Capitol Hill and led the rest of the route.

Ken Archer, 32, of Bowie, who had both legs crushed between two cars in an accident 10 years ago, finished first among the handicapped entrants. He covered the 26-mile 385-yard course in a wheelchair in 2:44.16.

Sparse but enthusiastic knots of spectators cheered the 9,753 runners on in their jaunt from the Iwo Jima Memorial in Arlington past the Pentagon and back again toward Key Bridge, from Georgetown to Capitol Hill, then through the monument area and Hains Point to the 14th Street Bridge and back across the river to the finish, also at the Marine Memorial.

Matthews, winner of the 1979 Honolulu marathon, has logged better times than he did yesterday, and he said he was not overly pleased with his performance. "But I'll take it," he said. "It is sweet to win."

A sciatic nerve injury a few months after the Honolulu run kept him out of marathons until this one, and he said he considers victory here "the first step on the road to 1984 (Olympics)."

Matthews, starting at just over a five-minute-mile pace, increased his lead over the rest of the field with each successive mile. At the four-mile point he was 80 yards in front; he was halfway across Key Bridge (eight miles) before the next runner set foot on it and he finished more than a quarter-mile ahead of his nearest rival surrounded by a platoon of bicyclists who accompanied him through the final stages.

"I was glad to have them. At least I had someone to talk to," said Matthews, a salesman for Ralston Purina. "I felt good right up until near the end. At about the 24-mile marker, I started losing my momentum, but by then I was almost at the end.

"I took over after the first mile and for the next 25 miles I was on my own. I know this is supposed to be a people's race, but I wish they would bring some (world-class) runners in. I would have liked someone to run with.

"It's a beautiful course, and the crowds were good. Except for Hains Point. It is so long and flat and monotonous. It is mentally very punishing."

Finishing second, 81 seconds behind Matthews, was Hank Pfeifle, 30, of Kennebunk, Maine, an industrial engineer for Nike Shoes. Pfeifle's time of 2:17.51 also broke the old record.

"I started running hard after about eight miles, and it felt like I was going to catch him," said Pfeifle. "I took command of the rest of the guys at about nine miles in Georgetown. I was feeling really strong, and I thought he would tire because he was out there all by himself. But I never got him."

After 20 miles, Pfeifle said, he realized he probably would not be able to catch Matthews. "But I kept running just so I'd be there in case he dropped," he said.

Chris Holm, 27, a hospital administrator from Rochester, N.Y., and winner of the Jersey Shores marathon two years ago, finished third, in 2:22.21, almost 4 1/2 minutes behind Pfeifle. Holm's wife, Karen, ran the first 10 miles of the race.

Lorenzoni, the women's division winner, said it was not until two weeks ago that she decided to enter the marathon. A member of the Charlottesville Track Club, she has been running competitively for nine years, frequently in 10-kilometer and 10-mile races. She won the Hecht's 10-miler in Washington last spring and finished fourth in Lynchburg.

As she crossed the finish line, Lorenzoni's legs buckled and she started to collapse. Aided to the medical tent, she was examined by physicians and released a few minutes later to attend the awards presentation.

"I was just a little tired," she said. "I am mainly a distance runner, but I had never run a marathon. Two weeks ago I decided to get the first one out of the way. I wanted to use this to qualify for Boston. I didn't know how to run this. The farthest I had ever run was 20 miles, and some people say the last six miles in a marathon are the toughest and some say the first 20 are the toughest."

Lorenzoni said she was unaware of her standing in the race until she passed Dillinger. After that point, spectators informed her she was first. Dillinger placed second among the women, in 2:53.48. Third was Norma Franco of Wheaton.

Archer, in the handicapped division, was actually the third to cross the finish line, but he had a 15-minute head start. The half-dozen wheelchair competitors and one entry on crutches were permitted to leave ahead of the rest of the field.

A veteran of 16 wheelchair marathons, Archer is a statistician at the Labor Department.