Indeed, numerous studies have suggested that wearing a bicycle helmet decreases the risk of head injury in the event of a bicycle crash. For example, one case-control study assessed the helmet-use patterns of 757 cases, 119 of whom were 13- to 19-year-olds, who had been treated for bicycle crash-related head injuries in one of seven major hospital emergency departments in the Seattle area (Thompson, Rivara, & Thompson, 1996). The pattern of helmet use among these cases was compared to that among 2,633 patients, 428 of whom were between the ages of 13 and 19, who were treated in the same emergency departments for other bicycle crash-related injuries. (The ethnic distribution of the study participants was not detailed in the published report.) The results suggest that adolescents who are not wearing a helmet at the time of a bicycle crash are nearly 2.5 times more likely to incur a head injury and 2.7 times more likely to incur a brain injury than are their helmeted peers. The findings for other age groups were similar. For all ages combined, not wearing a helmet at the time of a crash was associated with a nearly four-fold increased risk of severe brain injury. Helmets offered similar protection irrespective of whether a motor vehicle was involved in the crash. Several other studies, including a case-control study of Australian children ages 14 and younger (Thomas, et al., 1994) and one of bicyclists of all ages in England (Maimaris, Summers, Browning, & Palmer, 1994), have also reported a protective effect of helmet use on risk of head injury. Based on studies like those cited above, the CDC has recommended that every bicyclist should wear a helmet that meets current standards-in every riding situation (CDC, 1995).