One appliance and crew from Amersham attended, along with an officer.
One car was on its roof when they arrived. One woman, injured, and two children, uninjured but suffering from the effects of shock, were out when they arrived.
One man was out of the second car, uninjured.
The firefighters made the scene safe. The road was closed while they worked at the scene.
The woman was cared for by South Central Ambulance Service, and Thames Valley Police also attended.
