It happened just before midnight in rural Sullivan County near West County Road 700 North and North County Road 900 West.
Authorities say one of the ATV's collided with the back of the other one.
The ATV that did the rear-ending went into a ditch.
One person was airlifted to Methodist Hospital in Indianapolis.
The other person taken to Sullivan Community Hospital.
Names are not being released this morning.
Drugs and alcohol are not believed to be a factor in the accident, but speed is.
Copyright 2015 Nexstar Broadcasting, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.