About 1,200 walkers were at the opening ceremony in Northbrook on Friday, the Chicago Sun Times reported. Last year, there were 1,900.
The drop appears to be continuing fallout over the Planned Parenthood controversy earlier this year. Komen, which raises money for breast cancer, decided to cut a grant to Planned Parenthood's screening program but quickly restored it after a firestorm.
"Komen has had a tough year," Dr. Sheri Phillips, a spokeswoman for the group, said. "Although our participation is down ... we welcome any participant numbers because every dollar raised makes a difference in our efforts to put an end to breast cancer."