The 15th U.S. Marine Corps Marathon yesterday turned into a runaway victory for an inexperienced marathoner and included the death of a 19-year-old Boston University woman student, the second fatality in the history of the event.

Matthew Waight, 27, an electrical engineer from New Britain, Pa., who runs after work, broke away from the pack shortly after the start and much to his surprise stayed the course in front. The modest time of 2 hours 21 minutes 32 seconds carried him to his first marathon victory.

About 1:15 p.m., after 4 hours 15 minutes of running had brought her onto the 14th Street Bridge and a little more than two miles from the finish, Lisa B. Christensen, a sophomore at Boston University, collapsed. A midshipman in the Naval Reserve Officers Training Corps who was running with ROTC classmates, Christensen reportedly was unconscious with a weak pulse after the fall.

She was treated at the scene and taken by the Wheaton Rescue Squad to Arlington Hospital, where she also was treated. She died at 2:45 p.m., according to a hospital spokesman. A race official said reports he received indicated that Christensen may have suffered a head injury, but it was unclear last night whether that was related to the death. An autopsy was scheduled for this week.

In 1986, a 32-year-old Marine staff sergeant collapsed near the 15-mile marker and died of what was found to be undiagnosed "occlusive coronary atherosclerosis," a severe narrowing of the arteries that feed the heart. Just three weeks ago, a 31-year-old Alexandria man, an Army captain who was a seasoned runner, died as he approached the finish line in the Army 10 Miler here.

Yesterday's race was only the fourth marathon for Waight, who didn't think he was good enough to try out for cross-country or track at Iowa State, the NCAA cross-country champion last year.

"For some reason the pace was really slow," said Waight, explaining why he charged to the front. "I was really surprised there weren't many people around."

Waight looked fresh even at the end, when he was almost a mile in front, but said, "It was a real struggle the last four miles," especially the last quarter-mile uphill to the Iwo Jima memorial, the start and finish.

Running alone, he listened for comments that might tell of an approaching threat. But all he heard were words of encouragement and cheers -- for him.

Farley Simon, the 1983 champion and runner-up last year, came within 27 seconds of Waight but started walking at 20 miles when a recurring knee injury impeded his running. He was not able to finish. Robert Rollins, a corporal in the Royal Air Force, who was in sixth place at 23 miles, caught Barry Holder of Hagerstown at the tape for second place, 2:26:41 to 2:26:45.

Olga Markova, a 22-year-old Soviet Army sergeant from Leningrad, was the top women's finisher, in a race record 2:37:00 (the old mark was 2:41:48, set 10 years ago by Jan Yerkes of Buckingham, Pa.). Markova was the top woman in the recent Army 10 Miler and was the favorite yesterday. Speaking of the temperatures, which reached 75, she said through an interpreter, "This is great." At home, it's usually cold when she runs.

Suzanne Ray, 39, the women's runner-up in 2:44:48, also runs most often in the cold. She's from Anchorage. She won a road race in Alaska that entitled her to a prize: a trip to the marathon of her choice. She picked Washington, figuring she'd see some sights along the way.

"The first half was wonderful," she said. "The second half was terrible because of the heat. Especially for me, anything over 60 degrees is too hot."

Ray said she never saw Markova, but was on her own pace until Mile 21. "The last two miles was absolutely the pits, because of the heat," she said.

Ken Carnes, of Morningside, Md., took the men's wheelchair competition for the second straight year. His 1:40:22 was almost 14 seconds better than last year. Diana McClure, of Charleston, W.Va., was the women's wheelchair winner. "The hill at the end," she said, "was the hardest part for me."

Each of the some 13,000 participants had a story, and together they added up to a remarkable array as they journeyed the streets of Washington and Northern Virginia. The passing scene included: several blind runners, a woman who beat cancer, a woman who overcame an almost fatal car crash 11 years ago and had to use crutches as she covered the entire distance.

A host of Marines on M Street in Georgetown offered paper cups filled with drinks to runners coming off Key Bridge. Most drank, some poured the liquid over their heads, almost all threw the cups onto M Street.

A runner wearing maroon boxers and a sleeveless white undershirt had on a headset with a little aerial sticking up alongside his right ear. He carried a small camera and paused on M Street's double yellow line to photograph the people moving across Wisconsin Avenue.

Someone had placed a huge speaker in front of a second-story window and turned up the volume. It was music to encourage the runners, "Rocky"-like.

Although they were only halfway home, runners celebrated with smiles and upraised fists as they turned off First Street SE and onto C. They were going downhill, having finished the grind up Capitol Hill, the race's equivalent of Boston's Heartbreak Hill.

It's a deceptive ascent starting up Louisiana Avenue NW, but the slope steepens and is excruciatingly long and it takes its toll. It brought runners to a walk.

It does nothing for the morale while climbing the Hill to see a big sign that says "13" -- the 13th mile.

The big ticking clock at First and C NE -- 2:39:43, 2:39:44, 2:39:45 -- could tell a runner that the winner had already finished. But they knew, back in the long, straggly pack, there was more to this race than winning.

For those who needed morale boosting, this was the time and place for it. Stephen Grant of Washington sat on a grassy patch between Senate office buildings on First Street and blew his wooden train whistle as runners trudged up the incline.

Small, quiet celebrations among runners and their family and friends dotted the landscape at the finish. Participants had their muscles rubbed. They talked of their experiences. They were given medals, which they draped about their necks. Weary perhaps, they were winners in their own ways. Special correspondent Karl Hente contributed to this report.