Police are seeking witnesses to a collision at Longwarry on Thursday morning where a motorcycle and van, both travelling in the same direction, collided.
The 64-year-old Melbourne motorcyclist was airlifted to The Alfred hospital with serious injuries after he and a delivery van collided at 7.25am on the Princes Hwy.
The collision occurred about one kilometre east of the Sand Rd intersection.
The motorcycle and van were travelling east when the collision occurred.
Police said the van was driven by a 23-year-old Drouin man who was assisting police with inquiries. He was not injured.
The motorcyclist was airlifted from the scene with serious but non-life threatening injuries.
Police said both vehicles were extensively damaged.
Police are keen to hear from anyone who may have information that will assist investigations into how the collision occurred.