Introduction: Motorcycle crashes are associated with serious injuries and death including traumatic brain injury (TBI). Helmets are a protective factor; however states have begun to repeal helmet laws. Objective: Compare crash outcomes of operators and riders by helmet status. Methods: Statewide crash records were probabilistically linked with emergency department and hospital discharge data from 2003 – 2004. Descriptive analysis, chi-square tests, and logistic regression were used to describe factors associated with TBI. Statistical imputation was used to fill in missing values for all variables prior to analysis. Results: There were 1,991 riders in crashes. 84% were male; 54% wore helmets. 36% of motorcycle crashes were intersection related, 20% speed related. The largest age group was 20 - 24 years (22%) followed by 40 – 49 (16%). Over 1/3 of all riders were forty years or older. Younger riders had higher helmet usage rates than older riders (p=0.016). Older riders had larger engine sizes than younger riders (p<0.001). 53% of all riders were treated at a hospital. Helmet use was not associated with being treated at the hospital (p=0.31). However, the unadjusted odds ratio showed that unhelmeted riders were twice as likely to incur TBI compared to helmeted riders (p<0.001). Helmets also reduced the severity of TBI. 70% of helmeted riders had a moderate TBI, while 54% of unhelmeted riders had a severe TBI (p<0.001). Compared to riders without TBI, riders with severe TBI had higher hospital charges $70,974 vs. $10,834 (p<0.001). Increased adjusted odds of TBI were associated with alcohol, speeding, and single vehicle crashes; helmet use reduced the adjusted odds of TBI by half. Implications: Helmets are effective at preventing TBI. Policy makers and the media should be educated to preserve existing helmet laws. Latebreaker statement: Linked data were not available until May and analysis for project was completed in June.