Three crews (Gerrards Cross, Ruislip, Hillingdon) attended.
Firefighters were called to three cars and a heavy good vehicle involved in a road traffic collsion.
No persons were trapped and out of their vehicles prior to the arrival of the fire service.
Firefighters provided immediate emergency care to three males and one female who had sustained injuries before passing them into the care of South Central Ambulance Service.
National Highways were also in attendance.
The incident was then handed over to Thames Valley Police.