A mini-van carrying six children and two adults rolled over on Interstate 57 on the Far South Side.
It happened about 9:20 p.m.Sunday night in the southbound lanes, near 111th street.
An eight-month-old girl who was in the mini-van is in the hospital with life-threatening injuries.
Her twin sister, along with four other children and adults were not as seriously injured.
Police said alcohol was a factor, and charges against the driver are pending.
The lanes on the interstate have since reopened.