A man was seriously injured Sunday night at a CTA Red Line platform in Grand Crossing.
The man, 20, was found with cuts to his head on the platform in the first block of West 69th Street about 7:45 p.m., Chicago police said.
He was taken to University of Chicago Medical Center, where he was listed in critical condition, police said.
Police are investigating the incident as a battery.
No other information was available.