A study has been made of the extent to which bicycle helmets afforded protection in respect of the incidence and severity of head injuries in 36 matched pairs of cyclists, where one in each pair had worn a helmet and the other had not. The pairs were matched according to the age and se:​;​ of the injured, the type and cause of the accident, the kind of bicycle and the road conditions. Head injuries in the helmet area were less frequent and less severe for the cyclists who had been wearing helmets. The conclusion is that bicycle helmets, even simple ones, could be recommended for cyclists of all categories as they protect against head injuries, at least against head injuries of minor severity.