A Chicago Transit Authority bus hit a pedestrian crossing the street at Division Street and Kedvale Avenue about 10:50 p.m. Thursday, police said.
The bus was heading east on Division when it hit the man crossing at Kedvale, police said.
He appeared intoxicated, police said.
CTA Spokesman Molly Sullivan confirmed that a bus "came into contact" with a pedestrian in the street, and said the agency was investigating the incident.
Chicago Fire Department Chief Joe Roccasalva, a department spokesman, said the man was taken to Stroger Hospital in serious-to-critical condition.
The driver of the bus was taken in good-to-fair condition to Northwestern Memorial Hospital because he was "shaken up" by the incident, Roccasalva said.