The Chicago Marathon is one of long-distance running's marquee events, and there's no shortage of big-name runners who look to steal the spotlight.
Sunday's event is one of the five World Marathon Majors, which means the best runners will be out in force ready to take one of the biggest championships of the year.
The marathon, which started in 1970, has been won by 10 straight Kenyans in the men's contest and is the second-to-last major of the season before November's New York City Marathon.
Let's take a look at the runners who you need to know about heading into Sunday's 26.2 mile race.
Russia's Liliya Shobukhova is the main force in women's marathon running, and she's proved it in Chicago.
She has won the Chicago Marathon each of the last three years and looks to add another win to her streak in the Windy City.
Shobukhova, with the time of 2:18:20, completed the course faster than any woman in history in 2011 and will look to trim her record again Sunday.
You can't mention women's marathon running without Shobukhova's name coming up, and that's for a reason. The 34-year-old has won the Chicago Marathon three straight times and has finished in the top three in the London Marathon three times, including one win.
Kenya's Moses Mosop is one of the most notable marathon runners in the world right now, and it's in large part due to last year's Chicago Marathon.
Mosop finished at 2:05:37 in the 2011 event, marking the fastest time ever for a man to finish the Chicago course.
However, he's actually run a marathon 34 seconds faster than that time in Rotterdam, the Netherlands.
He was pulled out of the London Olympics because of a tendon injury and will look to prove Sunday that he's fully recovered and still a dominant force in marathon running.