The first thing veteran Marine Corps Marathon runners will notice about this year's course is an about-face.

For the first time, runners will head north on Route 110 toward Rosslyn after the gun sounds instead of south toward the Pentagon. In previous years, the course made at least one loop around the Pentagon before it really got going. (This year runners won't pass the Pentagon until Mile 24.) Instead, runners will turn left in Rosslyn just after the first-mile mark and head up Lee Highway for a mile and a half, turning around at what is now the highest point on the course (about 240 feet) and returning to the District along the George Washington Parkway.

After that, all becomes familiar as runners cross Key Bridge and go through M Street in Georgetown, climb two miles up Rock Creek Parkway and back (a 2001 addition to the course), then turn toward The Mall at the Lincoln Memorial near Mile 10.

After circling Capitol Hill -- the halfway point is on the south side of the Capitol -- the course goes through West and East Potomac parks and returns to Hains Point (Mile 18), notorious for too much wind and too few spectators. After crossing the Potomac for the second time, runners head south into Crystal City, where a large street party aims to boost spirits at Miles 22 and 23, a 2003 innovation.

The last change to this year's course is at the finish. Runners accustomed to passing the Iwo Jima Memorial and then running a few hundred yards more will be pleasantly surprised: They will get to stop. The finish area has been shortened, so that the memorial is truly the end of the run.

-- Bonnie Berkowitz