Security will be heightened following the deadly bombing at the Boston Marathon last spring.
But many of the estimated 45,000 runners are shrugging off concerns for their own safety.
The finish line in Central Park has become perhaps the biggest worry after two homemade bombs exploded near the finish line in Boston, killing three people and injuring more than 260.
New York for the first time is fencing off part of the western perimeter of the park for the race. Spectators will have to pass through security checkpoints to enter that area.