The crash, involving two cars, took place on the A41 Birmingham Road, at around 4am today.
West Midlands Ambulance Service sent four ambulances, two paramedic officers, a MERIT trauma doctor and a critical care paramedic to the scene.
Three women from one car, and a man from the second car, were all taken to Sandwell Hospital for further treatment.
One woman, a passenger in the car, suffered serious injuries.
The road was closed between the M5 junction one island and Halfords Lane for a number of hours due to the crash.
A spokesman for the service said: "Ambulance staff treated four patients in total who had been involved in the collision.
“The driver of one car, a woman, was found to have suffered injuries not believed to be serious. She was conveyed to Sandwell Hospital for further checks.
"Two other women from the same car were assessed by ambulance staff, both required treatment on scene with one suffering more serious injuries. The two women were conveyed to Sandwell Hospital for further care.
“The occupant of the second car, a man, was treated on scene for non-serious injuries before being taken to Sandwell Hospital.”