A man is being flown to Royal Perth Hospital after a two-car collision on Brand Highway, about 130km north of Perth.
RAC Rescue was sent to the crash near the intersection of Gillingarra Road in the regional farming area of Yathroo around 2.15pm on Saturday.
The chopper was forced to land on the road during the rescue.
A Department of Fire and Emergency Services spokesman said four appliances at the scene worked to free the male in his 30s, who was trapped in the vehicle.
Two other people were involved in the crash but had no injuries.
Volunteer Fire and Rescue Service firefighters also attended the scene.