Among them is a local runner who is legally blind.
Forty-seven-year-old Kurt Fiene is running the Boston Marathon for the 5th time.
"I'm hoping to run two hours and 46, 45, 46 minutes and make another PR and to win the visually impaired division," he said.
So far, he has completed 28 marathons.
"The upcoming Boston Marathon will be my twenty-ninth," Fiene said.
Fiene started running when he was a senior in college to lose weight.
"Just kept going and getting better and lost a lot of weight," he said.
He has been blind since birth.
"I have anordidea, which is no iris in the eye," Fiene said. "I can see, oh, about what people see at 200 feet I can see in 20 feet."
When running on the track, he can run alone.
"I can see the white lines to stay between during the day. I can run along if I'm not running fast, but if I'm doing something fast and I have to worry about traffic, I need somebody to run with so they can tell me if cars are coming or something if there's pot holes in the street," said Fiene.
Training for any marathon is an significant commitment.
"I'm running anywhere between 70 and 85 miles a week," said Fiene. "Anywhere from 18 to 22 miles."
Fiene has won a number of marathons in the visually impaired category. His personal best was in December at the California International Marathon where he finished in two hours and 50 minutes and three seconds.
His longterm goals is to go to the Paralympics.
"I was going to try to qualify for the Paralympics in '08, but I was going to try to qualify in the marathon but they didn't have the marathon for my visual classification, so I didn't qualify," said Fiene. "The upcoming Paralympics in 2012, I'm going to try to qualify in the 5000-meter and the 10,000 meter."
But for now, it's Boston.
"It's prestigious, you have to qualify to run it," Fiene said. "They do have a visually impaired category that I have won, I won last year the visually impaired category. Also, I like to go back there an defend my championship," he said.
Fiene was feature in April's Runner's World magazine.