Background. Previous case-control studies on bicycle helmet efficacy are mostly Anglo-Saxon, and based on data from the early 1990’s when hard-shell helmets were common. Methods. In France, the Rhône county (1.6 million inhabitants) is covered by a road trauma registry that includes ED visits, inpatients and fatalities. Over the 1998-2008 period, 13,797 cyclist casualties were identified (outpatients, inpatients and deceased). The injuries sustained were coded using the Abbreviated Injury Scale (AIS) for injuries to the head (AIS1+ and AIS3+), face (AIS 1+) or neck (AIS1+). The study uses a case-control design where the control group includes cyclists injured below the neck, i.e. not injured in the region associated with the helmet. We adjusted for age, gender and crash severity. Results. The adjusted odds ratios of helmeted vs. unhelmeted cyclists are: for AIS1+ head injuries 0.69, 95% CI=[0.59-0.81], i.e. reduction of risk by 31%; for AIS3+ head injuries, 0.30, 95% CI=[0.16-0.50] i.e. reduction of risk by 70%; for AIS1+ facial injuries, 0.72, 95% CI=[ 0.62-0.83], i.e. reduction of risk by 28%; and for AIS1+ neck injuries, 1.18, 95% CI=[0.94-1.47], non significant. Conclusion. This study confirms the protective effect for head and facial injuries, even though soft-shell helmets have now become more common. The reduction of risk is greater for serious head injuries. The study is inconclusive about the risk of neck injuries.