This study sought to quantify the fatal injury risks for motorcyclists associated with the riders blood alcohol concentrations (BACs).Method: Using a case-control study design with New Zealand data, fatal injury risk curves for motorcyclists and car drivers were modeled. A total of 142 fatally injured drivers/riders (cases) and 58,000 control drivers/riders were studied. For motorcyclists, there were 13 cases and 194 controls.Results: The rate of increase in fatal injury risk with increasing BAC was not found to be different for motorcyclists compared to car/van drivers. However, because the baseline risk for motorcyclists was already considerably higher than for car/van drivers, even modest amounts of alcohol were associated with very high risks for motorcyclists compared to sober car/van drivers. It was estimated that, relative to their sober risk, motorcycle riders at BAC = 0.03 percent have 3 times the fatality risk (95 confidence interval [CI] = 2.8-3.5) and, at BAC = 0.08, 20 times the fatality risk (95 CI = 15.0-27.3).Conclusions: Interventions focused on reducing the alcohol consumption of motorcycle riders are clearly required when the degree of risk even at low alcohol levels is as disturbingly high as estimated in the current study.