One man was stabbed and two others were hurt during a fight early Sunday on Michigan Avenue in the Loop.
Two groups of young people began arguing while walking past each other at Michigan and Wacker at 2:12 a.m., police said.
One member of each group began fighting, and a third person slashed two people in the abdomen and stabbed a third, also in the abdomen, police said.
The 21-year-old man who was stabbed is in serious condition at Northwestern Memorial Hospital, police said.
The two men who were slashed, ages 23 and 22, were also taken to Northwestern, where they are expected to be treated and released.
No one is in custody, police said.