In Te Anau, a person suffered serious injuries after a car and truck crashed on State Highway94, near the intersection with Sinclair Rd, at 2.30pm.
Two helicopters were sent to the scene and the patient was transported to Dunedin Hospital.
A St John spokesman was unable to provide details about the second patient's condition.
In Riverton, a car crashed into a power pole at 3.50pm on Riverton-Wallacetown Highway, opposite the Riverton Racing Club.
A police spokesman said the sole occupant of the car was uninjured.
A man was also taken to Dunedin Hospital by rescue helicopter in a serious condition after a crash between a motorcycle and car near Alexandra.
The crash happened on Crawford Hills Rd, about 9km from the intersection with Tiger Hill Rd, in Galloway.
Police and St John spokesmen could not confirm whether the patient taken to hospital was the motorcyclist.
Emergency services were called at 2.45pm and police, St John and fire services attended.
Earlier, two people were taken to Timaru Hospital with moderate injuries after the vehicle they were in overturned on State Highway 1, north of Glenavy.
A police spokeswoman said emergency services were called to the scene between Carrolls Rd and Te Maiharoa Rd about 1.50pm, after a vehicle rolled and came to rest in a paddock next to the highway.
