One person was killed in a head on collision just north of Alliston.
It happened Thursday morning just after 9.
Nottawasaga OPP were called to Scotch Line between 5th Sideroad and Shephard Avenue after two cars collided.
The 43 year old driver of the one car was killed instantly.
The man driving the other car had non life threatening injuries, while his female passenger was taken away by air ambulance in critical but stable condition.
The investigation is still ongoing.