Approximately 25,000 runners took part in the run through downtown Chicago.
Organizers posted the follow message on the events website:
"We are sorry to announce that Bret Michaels will NOT be able to take the stage this morning due to a sudden bout of severe dehydration and the flu. The XSport Fitness Rock 'n' Roll Chicago Half Marathon benefiting the American Cancer Society will still feature a finish line concert at the iconic Buckingham Fountain in celebration of each participant's accomplishment. The entire Rock 'n' Roll Marathon Series family wishes Bret a quick and healthy recovery and we look forward to his participation at our upcoming events.
The XSport Fitness Rock n' Roll Chicago half-marathon is a fun run that offers live, background music for extra motivation as participants run in support of the American Cancer Society.
ABC7 reporter John Garcia, a 15-year participant, ran the half-marathon and talked with some of the event's representatives and partipants at the finish line.
The Rock 'n' Roll half-marathon started at approximately 6:30 a.m. Sunday and took participants on a course of downtown roads, ending in Grant Park at Columbus near the Buckingham Fountain.
Runners enjoyed cool weather Sunday, unlike the severely hot temperatures that have marked the run in previous years.