A Marlborough man suffered a broken leg when the quad bike he was riding rolled down a bank.

The accident happened at Kekerengu, midway between Blenheim and Kaikoura, when the quad bike being ridden by the 52-year-old Kekerengu man rolled end over end about 3m down a bank.

The Wellington-based Westpac rescue helicopter arrived at the scene about noon and flew the man to Wairau Hospital in Blenheim for surgery.