Ryan Farquhar and Dan Cooper came off their bikes during the Supertwins race.
Race organisers said neither rider was thought to have suffered life-threatening injuries in the accident.
Farquhar, 40, from Dungannon, was airlifted by a police helicopter and was being treated in a Belfast hospital for chest and pelvic injuries.
Cooper, 28, from Stroud in Gloucestershire, was taken to the Causeway Hospital in Coleraine with shoulder injuries.
Farquhar is a well-known figure in motorcycling and has won five races at the North West.
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Racing was abandoned for the night following the accident and event organisers issued an update, saying both were in a stable condition.
Earlier, an air ambulance had been deployed when a rider was hurt during a practice session.
Nico Mawhinney from Castledawson crashed at the Mill Road roundabout and was transported to the Royal Victoria Hospital in Belfast. His injuries were described as not life-threatening.
There has been a campaign to get an air ambulance for Northern Ireland, and a fund to help achieve this is the official charity at this North West 200.