The roar of a thousand motorbikes has been echoing through Tasmanian streets.

Harley Davidson owners have descended on Launceston for a major rally.

The meeting of the Harley Owners Group, or HOG, has attracted enthusiasts from as far afield as Darwin, New Zealand and the United States.

This morning, they took over Launceston's York Park.

On Sunday more than 1200 bikes will rumble through the city on the Thunder Run.

HOG's Kim Williams says the party began early on the Spirit of Tasmania.

"They put on some special day sails for us so..the party actually started on the boat," she said.

Riders injured</h3>;

Two of the event's participants are in hospital after an accident near Poatina yesterday.

Police say a 57-year-old rider from New South Wales lost control of his motorcycle on a bend in the Great Western Tiers.

He is being treated for serious head and internal injuries and is in a stable condition.

His pillion passenger, a 55-year-old woman from New South Wales, has extensive facial injuries.

Her condition improved overnight.