Motorcycle riders are over 30 times more likely than car occupants to die in a traffic crash. While this fact is well known, specific issues of methodology in epidemiological motorcycle-injury research have been rarely researched. To facilitate more-valid research on motorcycle injuries, this article evaluates the current state of our knowledge on how we measure the population at risk of injury, completeness of case finding and identification, validity of crash/injury data sources, and completeness of information on important exposures such as alcohol consumption, helmet status, crash severity, and crash speeds, as well as problems of existing injury severity scales and statistical analyses for correlated injury data.