Police are warning motorcyclists to take extra care after the number of fatalities in the Avon and Somerset force area reached a nine-year high.
In 2004 there were 21 fatalities involving motorcycles, a rise of 91% on the previous year.
A force spokesman said many of these could be avoided by bikers taking more responsibility for their safety and riding in a "more responsible manner".
He also encouraged retailers to offer appropriate safety training.
The spokesman added men aged between 30 and 50, riding 125cc-plus motorbikes tended to take excessive risks in terms of speed and lack of judgement.
He also suggested those returning to riding after a break should consider the power of the bikes they are buying.