BOSTON — Joan Benoit Samuelson can see the finish line, and this time her legs are steady.

The 50-year-old Olympic gold medalist plans to run in her last competitive marathon on Sunday in the trials that will choose the U.S. team for Beijing. Deena Kastor, who won the bronze medal in Athens in 2004, is a heavy favorite to make the team. Two more berths are available for a group that includes Mary Akor, Samia Akbar, Zoila Gomez and Kate O'Neill.

Samuelson won the inaugural women's Olympic marathon in 1984, running into the Los Angeles Coliseum to the cheers of the American fans. She may not be a threat to return to the Games, but almost 30 years after the first of her two Boston victories the women's running pioneer is being hailed in her adopted hometown.

"Joan, so many years later, continues to inspire so many people, supporting women and distance running in general," said Kastor, the only other American woman to medal in the Olympic marathon. "Even before I started running, she was an inspiration to my entire household. It's a great honor to be a part of the event with her."

Although "The Star-Spangled Banner" hasn't been played at the Boston Marathon since Greg Meyer won in 1983, this year's Olympic trial gives organizers and fans a chance to salute an American winner.

Sunday's race will follow a course that loops through Boston's Back Bay, along and across the Charles River into Cambridge, starting and ending at the Copley Square finish line used by the traditional race for most of the last 112 years. The regular Boston Marathon will continue its long run as usual on Monday, Patriots Day in Massachusetts, and Samuelson will fire the starting pistol for the women.

Samuelson won the traditional race twice, in 1979 and 1983, the first time as a 21-year-old Bowdoin College senior in a Red Sox cap. She won the Olympic trials in 1984 less than three weeks after arthroscopic surgery on her knee.

"I wasn't even sure I was able to go the distance. I still can't understand how I was able to," she said this week. "So that would have to be the race of my life."

But in Los Angeles, she may have topped it.

"I remember saying to myself, 'Are you really prepared to come into the Coliseum and finish first,'" she said, describing her legs getting wobbly for the trip around the track. "I was really wondering if I can stand up. I was overcome with emotion."

Almost 51, Samuelson knows that she cannot compete with the younger athletes who run faster and train harder than she ever could. Although her personal best of 2 hours, 21 minutes, 21 seconds would be competitive, it was 23 years ago; her qualifying time of 2:46:27 puts her on the fourth page of four in the media guide list of possible entrants.

"There's a lot of technology in the sport, a lot of emphasis on heart rate and things like that," she said. "I've just always done it by the seat of my pants."

But it wasn't the competition, it was struggles with her own body that cooled off Samuelson's love of running for a while. She has always had a leg-length discrepancy that began to catch up with her, causing calf and hamstring problems that kept her from long training runs.

Last November, she got her body straight and set her mind to returning. By January she was ready to increase her effort, but she found herself making excuses _ usually the Maine weather _ for not stepping it up. "I just kept putting it off," she said.

One day in the first week of the new year, she looked out on a wind chill of minus-23 degrees, with snow and ice covering the roads, and decided it was time.

"I said, 'What am I doing out on the road?'" she said. "But I knew if I didn't get out there that day it wouldn't happen."

Her training complete, Samuelson has modest goals for Sunday: to finish in under 3 hours.

"I'm not trying to prove anything," she said.

She's already done that.