Background: Head injury is the leading cause of death and long term disability from bicycle injuries and may be prevented by helmet wearing. We compared the pattern of injury in major trauma victims resulting from bicyclist injury admitted to hospitals in the State of Victoria, Australia and South-West Netherlands, with respective high and low prevalence of helmet use among bicyclists. Methods: A cohort of bicycle injured patients with serious injury (defined as Injury Severity Score > 15) in South-West Netherlands, was compared to a cohort of serious injured bicyclists in the State of Victoria, Australia. Additionally, the cohorts of patients with serious injury admitted to a Dutch level 1 trauma centre in Rotterdam, the Netherlands and an Australian level 1 trauma centre in Melbourne, Australia were compared. Both cohorts included patients admitted between July 2001 and June 2009. Primary outcome was in-hospital mortality and secondary outcome was prevalence of severe injury per body region. Outcome was compared using univariate analysis and mortality outcomes were also calculated using multivariable logistic regression models. Results: A total of 219 cases in South-West Netherlands and 500 cases in Victoria were analyzed. Further analyses comparing the major trauma centres in each region, showed the percentage of bicycle-related death was higher in the Dutch population than in the Australian (n = 45 (24%) vs n = 13(7%); P