Introduction: Previous studies of motorcycle injuries show that helmet use is associated with a decrease in head trauma. Understanding patterns of helmet use is important in selecting and assessing injury prevention strategies.

Methods: All 470 motorcyclists presenting to either of two regional Level I trauma centers from 7/93 through 12/95 comprise this case series. Thirty-three patients were excluded due to unknown helmet use or outcome, and 50 due to age under 18 years (for whom helmet use was required by state law).

Results: Of 386 patients, 42% wore helmets, and 58% did not, with no difference in the mean ages of the groups. 13% of patients were women (n = 50), and 10% were passengers (n = 38). Women were 25 times more likely than men to be passengers (95% CI: 11 to 50), and passengers were 5 times more likely than drivers to not wear a helmet (95% CI: 2 to 16). Helmet use was not related to sex, even when the data were controlled for driver vs. passenger. Of 265 patients assayed for ethanol, 30% had >100 mg/dL, 7% had <100 mg/dL, and 63% had none. Non-helmeted patients were 3.6 more likely than helmeted ones to have detectable ethanol (95% CI: 2.0 to 6.5), but there was no association with sex or age. The mean ethanol level was 80 mg/dL in non-helmet users, and 24 mg/dL in helmet users (p <0.001). 39% of non-helmeted patients were legally intoxicated (ethanol > 100 mg/dL), compared to 11% of helmeted ones.